Blue Mistflower - Love It or Fear It?

Blue mistflower (Conoclinium coelestinium). Last year, this started as just a tiny quart-size plant. This year, it's on the march!

As with other fast-spreading yet herbaceous perennials (e.g., mountain mint), I'm not quite sure about the best way to use blue mistflower (Conoclinium coelestinum) in my garden.

On the bright side, as I wrote last November, it has a nice long autumn bloom season with flowers that attract pollinators.

On the other hand, as Tammy and Jason both pointed out last year, blue mistflower likes moisture. Although it's planted in heavy clay that gets sodden in winter and early spring, the area also bakes in summer. Of the three clumps I had growing last year, it looks like only one clump (the healthiest and strongest) came back this year.

That surviving clump has expanded dramatically - from a 3.5-inch pot to probably close to 4 square feet in about 18 months. I recognize that I kvetched in a recent post about some groundcovers - Epimediums and partridge berry -  spreading too slowly.

How can I turn around and complain about a groundcover spreading too fast? Aren't groundcovers supposed to cover ground.

Sure they are.

But as with many things in life, I think there is an ideal happy medium here. I don't want a 'groundcover' that pokes along, only extending its coverage by a couple of inches per year.

But I also don't necessarily want a groundcover that races across the property, smothering small buildings in a single season.

I'm much more leery of aggressive plants if they're exotic. I don't want to be responsible for unleashing havoc on the local ecosystem. It's one of the reasons why I gave plants like blue star creeper, creeping raspberry, sweet woodruff and Ajuga the heave-ho.

(Well, I'm trying to evict Ajuga from the garden. It's putting up a heck of a fight to stay.)

I'm much more willing to tolerate aggressive plants if they're native and/or easy to remove. For example, wild strawberry (Fragaria virginiana) spreads pretty darn fast, but (a) it seems to spread only via above-ground stolons (so I can at least keep track of its spread versus those plants that extend their territory via underground rhizomes), and (b) it seems very easy (so far) to uproot any clumps that grow where they are not wanted.

When the blue mistflower gets a little taller, I plan to go out after a rain and see how hard it is to pull out some stems along the edges of the clump. Basically, I want to see how much of a struggle it will be to keep this in bounds.

(Update - I went and tried this and the blue mistflower stems at the edge of the clump seemed quite easy to pull. That makes me feel a bit more confident that I could keep blue mistflower from overwhelming other nearby plants...)

If I do let it stay and it romps through the back garden, I envision a lot of late winter or early spring maintenance.

It's not such a big deal chopping down stems on a few clumps of rose mallow (Hibiscus moscheutos), but I think it's another matter entirely to find a way to deal with 100 square feet of a tough-stemmed herbaceous and rhizomatous perennial.

For anyone who has a large stand of blue mistflower or any other aggressive perennial (e.g., one of the rhizomatous goldenrods, a spreading Monarda or a mountain mint), how do you handle winter clean up of large swaths of dead stems. Do you cut back by hand with a bypass pruner or shears? Do you use a mower?

Blue mistflower leaves, up close and personal

Then there's the issue of blue mistflower being deciduous/herbaceous. It dies back in winter and didn't make an appearance this year until late March / early April. If it covers a lot of ground in spring, summer and fall, that means a lot of bare ground from late autumn to early spring. I worry about weeds getting a toehold in that bare dirt.

That's why I've gravitated toward low-growing evergreens ('Biokovo' geranium, wild strawberry, golden groundsel, Robin's plantain, etc.) in my search for ideal groundcovers.

Anyway, blue mistflower is still in the garden for now. If you grow this plant - or something similar in habit - I'd love to hear how you integrate it into your garden to enjoy its assets without having it become a maintenance nightmare.

Some disappointments - rose verbena, toad lily, epimediums and partridge berry

I recently wrote about a couple of native groundcovers - golden groundsel and rose petty - that have impressed me with their performance.

(That doesn't mean I won't change my mind with a few more years of growing experience under my belt. That's happened before many times. But right now, color me impressed. And I like to think that I've learned to wait at least a little longer before passing snap judgments.)

Anyway, it's not all sunshine and roses in the Garden of Aaron.

I've been forced to face some disappointments this spring.

And since one of the main goals of my blog is to help others learn from my mistakes (and successes), I thought I'd share these disappointments with you:

Rose verbena (Glandularia canadensis) not looking its best

Rose verbena, Glandularia canadensis - Relatively easy to find at local nurseries (though typically in the form of the 'Homestead Purple' cultivar...which may or may not actually be a hybrid), I'd heard warnings that rose verbena liked good drainage and could die if forced to overwinter in heavy, wet clay soil (which I've got in spades).

Interestingly, rose verbena seemed to survive our relatively mild winter without too many problems.
It even stayed somewhat evergreen and started blooming early in the spring. I saw a swallowtail butterfly nectaring on one of the plants, which made me happy.

But soon, one by one, the rose verbena plants started turning brown and crispy. I'm calling this a failure and assuming either (a) it's a very short-lived perennial (practically an annual) or (b) it needs much better and lighter soil than I can provide.

It's a shame, because I've been trying to find effective, native groundcovers, and rose verbena had some appealing characteristics - it's fast growing, semi-evergreen in zone 7, heat and drought tolerant, and has a long bloom season. Unfortunately, it doesn't seem to have the toughness or longevity I need in a groundcover.

Don't see anything here?
That's because I mowed down the old Epimedium foliage a month or two ago and the new slow-to-emerge foliage and flowers got chomped by something (probably a rabbit). Which is a little odd, since the rabbits never bothered Epimediums much before...

Epimediums, fairy wings, horny-goat weed - I'd had good luck with a hybrid called x perralchicum 'Frohnleiten'. In fact, I came to like this herbaceous, evergreen-to-semi-evergreen groundcover so much that I featured it on its own blog post in May 2015.

Most sources recommend cutting off old Epimedium foliage before the new foliage emerges. In years past, I done this with bypass pruners, but as the patch grew a bit larger, I decided to try mowing down the old foliage this year.

I don't know if the mower was to blame, but the new flowers and foliage seemed slow and sparse to emerge this year. I was just starting to see a fair amount of foliage when something - I think a rabbit - came and devoured everything.

That's interesting, because in years past, the rabbits have seemed completely disinterested in Epimedium. Even before my Epimedium displayed a vulnerability to herbivores, I had soured a little on it. The flowers are pretty, but short-lived and rather inconspicuous. It grows slowly, which can be a good thing (you won't have to worry about it conquering a garden bed while your back is turned), but it also means that you'll be waiting a loooooong time for this groundcover to cover some ground and start displacing weeds.

Although 'Frohnleiten' has grown fairly well here in Middle Tennessee, the other Epimediums that I tried (x warleyense and x versicolor 'Sulphureum') have not fared nearly as well. They haven't been growing as long and I've heard that Epimediums are notoriously slow to settle in, but Sulphureum disappeared during last year's autumn drought and hasn't been seen since. The warleyense hybrid hung in there, but barely sent up any new foliage so far this spring, and what did emerge was eaten just the same as the 'Frohnleiten'.

I haven't given up quite yet on my Epimediums at this point. If they recover from the rabbit attack and send up new foliage, I'll be tickled pink.

And if that does happen, next spring I think I'll just leave the old foliage to decompose naturally without cutting it at all. I tried that last year, and even though the rough, leathery, tattered old foliage detracts a bit from the freshness of the flowers and new leaves, it also provides a contrast that makes it easier to see the bronzy new foliage on 'Frohnleiten' (which can otherwise be a challenge to notice against a background of mulch or dirt) and also I suspect that the old foliage deters herbivores from chowing down on the new growth.

Still, even if my Epimediums do stage a comeback, I can't imagine getting any more at this point, and I'd only consider recommending them for a very small garden where the slow horizontal growth rate would be an asset, or a larger garden where groundcover needs were somehow minimal.

Partridge berry (Mitchella repens) does cover ground, but it's a pretty subtle plant. You might easily overlook it in a large garden. And the ultra low-growing foliage doesn't block all the weeds.

Partridge berry, Mitchella repens - I've gone back and forth on this plant. Much like with Epimedium, one of my main complaints would be that it's a sloooooow spreader. And the leaves are tiny. Which means that even where it does spread, weeds can still force their way through.

A close-up on the partridge berry. Note how the small weed - probably some type of Oxalis - has poked its head through the partridge berry foliage without any difficulty. Having a ground-hugging plant like partridge berry has some advantages - there's no need to chop down old stems or seedheads, you won't have to worry about it swamping any nearby plants - but it does limit the weed-blocking role it can play in the garden.

That said, I don't want to be too harsh on this native plant. It blocks some weeds. It's essentially evergreen in Middle Tennessee. It had a few tiny flowers last year, though if it produced any berries, I didn't notice. I certainly wouldn't discourage anyone from using this, nor am I contemplating removing mine. In fact, I just added another clump of this plant to the garden this spring.

But I'm a bit disheartened at its slow spread and imagine it will be many years (if ever) before I have a nice, thick, noticeable clump like this.

Again, if you have a very small garden or a garden with only a small patch of bare ground to cover, this might be just the ticket.

PS - Partridge berry is so diminutive that I've often wondered how it avoids getting smothered by leaves in its native woodland habitat. According to Brooklyn Botanic Garden, it generally grows on steep slopes where fallen leaves slide away. If you have it growing on flat land (like I do), you might need to brush away leaves to let it see the light.

Chomped toad lily.

Toad lily, Tricyrtis hirta 'Miyazaki' - Bought this one on a whim during a nursery visit this spring. Turns out that it makes excellent rabbit food. (Or food for some other herbivore, but the signs point to a bunny.)


How about you? Any groundcover / perennial disappointments recently? Or happy surprises? 😎

Good native groundcovers - Robin's plantain and golden groundsel

I've trialed a lot of groundcovers and made a lot of mistakes over the past 6 years in my efforts to find that magical plant that will cover ground and suppress weeds, but not be too aggressive/invasive or too much work to maintain.

Here are two promising evergreen / semi-evergreen candidates that have performed well so far. The fact that they are both native to this part of Tennessee is a big bonus.

Packera obovata, golden groundsel, fully evergreen through this past (relatively mild) winter. 
(I tried growing another Packera - P. aurea - last year, but it did not seem as tolerant of heat and drought, even in partial shade, as P. obovata.)

Erigeron pulchellus, Robin's plantain As you can see, the Robin's plantain gets a bit more tattered over the winter compared to the golden groundsel. Still, in my experience over the past few years, the old foliage tends to decay naturally without any intervention on my part, and the plants will look much better soon as new foliage appears. (Yes, the flower head here looks a little strange...a bit like a conjoined twin. That's not the normal flower appearance, as you can see below, but it's not that uncommon either with Robin's plantain.)

I think golden groundsel needs partial to full shade in hot summer climates like Tennessee, and Robin's plantain also thrives in some shade, but I'd like to try it in sunnier spots too to see how it performs. It's relatively easy to divide and transplant Robin's plantain in early spring or early autumn, but I've learned the hard way that divisions are unlikely to survive if you wait too long in either season.

Covering a Lot of Ground - A Long Ramble

Aguga genevensis seems a bit less thuggish than the commonly sold A. reptans. In a sense, the uniform growth habit is beautiful, but it's very low-growing (which means that weeds do sometimes pop up through the foliage) and I do get nervous about controlling its spread or removing any bits that spread too far. UPDATE 4/17 - Decided all the exotic Ajugas were too aggressive, forming monocultures and not offering enough ecosystem benefits. Tried to rip them out. This patch right here was the largest and the hardest to remove. Spent hours digging it out over the winter. This spring, a good bit has come right back from roots I missed. Argh!

I feel I've learned a lot over the past 5+ years gardening in Middle Tennessee.

I've found all sorts of plants - trees, shrubs, perennials and annuals - that can survive and even thrive in awful compacted clay with a tough-love regimen of low-input style gardening (i.e., benign neglect -- no fertilizer, supplemental water only under severe drought conditions).

Yet, I still spend a lot of time these days thinking about how to cover bare ground.

Ajuga tenorii 'Chocolate Chip' is probably the easiest-to-control Ajuga, but the flip side is that it spreads the slowest. UPDATE - It does spread more slowly than A. genevensis or A. reptans, but it offers just as few ecosystem benefit, little aesthetic appeal, still forms a dense monoculture and still resists removal (although these clumps were not as established as A. genevensis and thus have not come back as vigorously after my attempts to dislodge them).

What I mean is this -- Imagine that you have a large lawn (like many American homeowners). You recognize that your lawn isn't doing much for wildlife and that it's not exactly eco-friendly. (In most parts of the country, lawns require supplemental water, fertilizer, reseeding and so forth to make them look good. And then there's the mowing and the string-trimming and so forth.)

So you want to put in a big garden bed - some trees, some shrubs, some perennials - and get rid of let's say 1/4 or 1/2 your lawn in one fell swoop.

Splendid.

But what do you use to cover ground among the plants to prevent the new bed from becoming a weedy mess?

One option is to put down mulch. (See Deb's Alabama gardening blog for a nice overview of the pros and cons associated with different types of mulch.)

That may actually not be a bad choice for at least a couple of years until the trees, shrubs and perennials get established and hopefully begin shading out or occupying a good bit of the soil to outcompete the weeds (or at least give them a run for their money).

But in many cases (at least in my neck of the woods), people seem to get stuck on the 'wide of expanses of mulch among a few isolated plants' look. Not only is it ugly and bare looking (IMHO), but it requires annual or semi-annual remulching and (I suspect) pre-emergent herbicides to keep weeds from filling in all that bare space.

Also, if the landscapers apply too much mulch repeatedly, I don't think it's especially healthy for whatever plants do live in those beds, which can get buried in mounds of wood chips.

But what other options do you have?

Theoretically, you could scatter some seeds and hope that floriferous annuals fill in the space until your larger plants have matured. I'm thinking of plants like Tagetes patula (French marigold) or Zinnia elegans (zinnia), perhaps a dwarf cultivar of Helianthus annuus (sunflower).

But there are some drawbacks to this plan. If you are spreading annual seeds, you can't mulch too heavily (or spread pre-emergent herbicide, for obvious reasons). The right conditions for wildflower seeds to germinate might also be the right conditions for weed seeds to germinate, so you'll need to hand-weed the bed until the annuals get going and (again) start shading out the soil and outcompeting weeds.

Some annuals can grow quite tall and bushy. This year, I had about 1,000 volunteer Cosmos (C. bipinnatus) plants show up. I don't think I'm exaggerating. Having a lot of ground to fill, I let many of them grow into a mini Cosmos forest.

It was lovely in June and July when many of the plants were in full bloom.

But packed together, competing for sunlight and nutrients, many of the plants did not bloom at all. The dense growth attracted pests (spittlebugs, mainly) which drained the plants of vigor. Stressed by heat and humidity, many of the plants started to die - turning brown from the ground up.

I could have uprooted these plants, but I decided to try to cut them off at the base, so that their roots would decompose in place and hopefully jumpstart the process of soil conditioning and improvement.

Many of the seeds were probably eaten by finches before I started culling the Cosmos. Many other seeds are probably still on the seedheads that I scattered through the beds, so I am sure there will be a whole lot of Cosmos seedlings next year too.

But next year I plan on doing a lot more winnowing early in the year when the Cosmos seedlings are still just a few inches tall. I'll hoe or chop or pull them at that stage when I don't need a lopper or a bypass pruner to cut them down.

That's not to say I'm giving up on annuals (or short-lived perennials) entirely. I'm just saying that I think that certain plants like Gaillardia x grandiflora (blanket flower) or Chamaechrista fasciculata (partridge pea) might be a bit less troublesome to deal with at the end of the season (and/or might have a longer flowering season for me than Cosmos bipinnatus). Of course, your mileage will vary and your ideal annuals will differ from one climate and zone to another...

You can use a mass planting of blanketflowers (Gaillardia x grandiflora) as a groundcover. But Gaillardia has a reputation (deserved, it seems) for being a relatively short-lived plant. Odds are you may only get 2-3 years from a specific Gaillardia plant. Still, if your blanketflowers self-sow (as mine sometimes do), then they could continue to collectively cover ground even as individual plants die out.

But are annuals even a wise choice? What are the other options besides annuals and mulch?

Well, the two other obvious choices (am I missing any others?) would be perennial groundcovers and shrubs.

In both cases, of course, there's certainly a possibility that a weed will germinate and grow underneath another plant, but in my limited experience, weeds are much less problematic if you have a bed chock full of other garden plants.

I have a few shrubs like Vibnurnum x pragense (Prague viburnum), Viburnum dentatum (arrowwood viburnum) and Myrica cerifera (wax myrtle) that do seem to shade out the ground beneath them pretty well and impede weed germination.

The evergreen foliage and bushy habit of this wax myrtle (Myrica cerifera) seem to do a good job of shading the soil and discouraging weeds.

I don't see many weeds growing beneath the evergreen 'canopy' of this Prague viburnum (Viburnum x pragense)

Of course, by their nature, upright or even rounded shrubs won't cover a massive amount of ground, at least not very quickly, because they want to grow up as much as (or perhaps even more than) they want to grow out. Other shrubs I grow such as Philadelphus 'Natchez' (mock orange) (UPDATE - I removed the mock orange from the garden in autumn 2016 and replaced it with a transplanted Viburnum dentatum) and Hibiscus syriacus (rose of Sharon) are even more upright. They have a very small 'footprint' that makes them easy to fit into a garden bed, but I think this upright form doesn't do much at all for impeding weeds around their base.

So why not get a sprawling shrub with a groundcover habit? I've tried something like that a few times and often I have been less than pleased with the result. Ultimately, I've chickened out and shovel-pruned several of these groundcover-type shrubs.

So far, that list of gone-but-not-forgotten includes Jasminum nudiflorum (winter jasmine), Rosa setigera (climbing prairie rose) and most recently Rhus aromatica 'Gro-Low' (fragrant sumac).

The problem for me is that all of these plants were (a) too rambunctious and (b) not really dense enough to block weeds.

Take the Gro-Low sumac. In a few years, a single one of my plants probably sprawled about 10 feet across -- and that was with multiple prunings. This year, the pace of growth really picked up and I couldn't keep the plant within the bounds of its bed even with pruning it every few weeks. I think there were stems that put on 6 feet of new growth this year alone.

Now I recognize that for some people, a wildly rambunctious and fast-growing plant could sound exciting. Perhaps you want to remove all the grass on a large hillside and replace it with Gro-Low sumacs, letting them sprawl out and hopefully rapidly cover the hillside.

Well, recall the story of Mickey Mouse and the broomstick in Fantasia. Even when the fountain was overflowing and the whole castle was flooded, the broomstick was hell-bent on adding more water.

When the Gro-Low sumac reaches the end of its designated area, will it stop? I don't think so. Perhaps it would eventually slow down as the ends of the branches got further and further from the core... except that Gro-Low sumac (like both winter jasmine and the climbing prairie rose) has a tendency to tip-layer ... meaning that where branches make extended contact with the soil (a frequent occurrence in low-growing, sprawling plants), those branches tend to develop roots. So in a sense, the 'root ball' of the plant continuously expands, the plant gets stronger and sends up new shoots, which curve back down, make contact with the soil, develop new roots and the cycle continues.

One option (I considered this before shovel-pruning the sumacs) might be to conduct a drastic pruning on the plants every winter, pruning them back close to the ground. It seems to me that there's a chance such continuous drastic rejuvenation pruning might weaken and then kill the plant eventually, but even if it did survive, you'd be looking at multiple months without much soil coverage - which would enable weed germination or (in our imaginary slope context) soil erosion.

The bare space you see here was previously covered by three Rhus aromatica 'Gro-Low' shrubs. In three years, these shrubs filled the space and strove continuously to expand beyond the confines of this bed.

Here's some of the Gro-Low foliage that I cut up while removing the plants. I'm letting the foliage dry on the back patio. When the leaves get brittle, I'll sweep them off the plants so their nutrients can go back to the soil. I'll probably end up taking the branches to our local county-operated 'Convenience Center' where they'll be turned into mulch.

In fact, even without rejuvenation pruning, a deciduous shrub like Gro-Low sumac doesn't necessarily offer any groundcover protection in the winter months. If it sheds its leaves in November and doesn't leaf out until April (here in Tennessee), you're looking at 6 months of bare branches and bare soil beneath. Weeds will (did) germinate beneath the shrub. Some of them may be shaded out when the shrub leafs out in the spring, but others will (did) simply grow above the shrub's canopy. And it's not fun or easy to get in amid a tall, woody groundcover to try to pull weeds. (The problem seems even worse amid a tall, woody and thorny groundcover, which is one reason that I ended up shovel-pruning the Rosa setigera.)

You can of course go with an evergreen groundcover shrub. Depending on your climate and soil, you may have quite a few options in this category or you may have only a few (or perhaps none at all). In Tennessee, two of the best options I've found so far that fit this bill would be Juniperus virginiana 'Grey Owl' (some people think 'Grey Owl' is actually a hybrid juniper, but Missouri Botanical Garden lists it as a cultivar of our native eastern red cedar) or the prostrate version of the Japanese plum yew (Cephalotaxus harringtonia).

Due to their evergreen nature, not only are they prettier in the winter (IMHO), but they also seem to do a much better job of covering the soil and discouraging weeds. As far as I know, neither of these plants actually roots into the soil as it spreads, which makes it much easier to prune the shrubs back if they start growing out of bounds. Since they spread at a reasonable pace (perhaps 12 inches per year), I have not found it especially challenging to control or direct their spread so far.

'Grey Owl' juniper

Beyond woody groundcovers, there are also perennial herbaceous groundcovers, and I do think this category offers some excellent possibilities -- with a few caveats of course.

I think the biggest caveat is picking the right plant. I've tried certain perennial groundcovers (Pachysandra procumbens, Hexastylis arifolia) that have struggled and died (or barely survived) rather than covering any ground.

Conversely, I've tried some exotic groundcovers like Ajuga reptans, Rubus calycinoides (creeping raspberry), Pratia pedunculata (blue star creeper), Ceratostigma plumbaginoides (hardy blue plumbago), Galium odoratum (sweet woodruff) and Teucrium chamaedrys (creeping germander) that all turned out to be more trouble than they were worth.

What makes an undesirable groundcover?

As with certain woody plants, rambunctiousness definitely comes into the picture. We all think we want a fast groundcover to cover lots of ground quickly, but what happens when the groundcover reaches the limits of whatever space you want covered? Do you want a constant battle with a bully that's trying to take over your whole garden -- and perhaps a neighboring natural ecosystem to boot?

What other tendencies, behaviors or traits might make a groundcover undesirable in my book?

1) Underground operations -- Some groundcovers look innocent and well-behaved above ground, while secretly spreading a wide web of roots below the soil surface. It can be very hard to control the spread of these plants. Also, if you do decide to try to uproot a groundcover that has spread its roots far and wide, there's a good chance you'll miss a piece of root that can regenerate a whole new plant when you're not looking. And if the whole top inch or two of soil is inundated with the roots of the groundcover, other plants in the bed could have difficulty competing for nutrients and other resources.

2) Woody bits -- In my experience, it's necessary to cut back the woody old growth on plants like creeping germander and creeping raspberry. That's not fun and it's certainly more tedious than dealing with a purely herbaceous groundcover.

3) Not too aggressive -- As with much of gardening (and life in general?) there's a bit of a Catch-22 here. You want a plant that's at least somewhat assertive. You don't want a pushover that lets any weed muscle its way through, but you (or at least I) don't want a plant that's going to dominate a bed and romp over everything else in its path, including small shrubbery (I'm looking at you Melissa officinalis, lemon balm).


So which herbaceous groundcovers have fit the bill so far for me here in Middle Tennessee? So far I've had good luck with Fragaria virginiana (wild strawberry), several Epimedium species, Geranium sanguineum (UPDATE 4/17 - Uh no. G. sanguineum actually turned out to be too aggressive and very hard to uproot/eradicate mechanically when I did decide to give it the boot) and Geranium x cantabrigiense. The threadleaf coreopsis (Coreopsis verticillata) has been very nice too in certain places, although it seems a little picky. I've got six plants that are absolutely thriving in full sun and amended soil, but ones in full sun and solid unamended clay are struggling and another patch in shade seems to be dying out. Rose verbena (Glandularia canadensis) might work out too, although I've heard that's also short-lived. (UPDATE 4/17 - Yep, ended up removing most of the threadleaf coreopsis too. It seems both short-lived and paradoxically aggressive. At least the roots are much easier to pull out than those of G. sanguineum. That makes me much less concerned about leaving some bits where it is performing well. It only makes a seasonal groundcover though, since it dies back to the ground in late autumn and doesn't return until early April. Rose verbena didn't work either. I liked it, but the short-lived part turned out to be very true for me. All of my rose verbenas pretty much behaved like annuals.) 

Epimedium species make great groundcovers for shade. They spread very slowly - which is not great for covering ground, but does seem to make it easy to control their spread. They don't form a mat of foliage, which makes me think you could have tall perennials (coneflowers? agastache?) popping up through the Epimedium if you wanted. They're also evergreen, which is nice both in terms of sheltering the soil in the winter and giving you something green to look at when much of the rest of the landscape is brown and/or bare.

It's my first year trialing our native wild strawberry - Fragaria virginiana. as you can see, it doesn't have the uniform growth habit of an Ajuga, but it ends out runners and forms patches of plants here and there. It's too early for me to give a verdict on the plant yet, but so far I find it charming and it seems easy to uproot any runners that spread too far.

I think many of the perennial geraniums like cooler temps than those we have in Middle Tennessee summers, but Geranium sanguineum seems able to beat the heat. It looks good here in partial sunshine, but seems able to survive even in nearly all-day sun. This geranium species also seems to spread quickly, but I've found it very easy to pull up patches that start encroaching on other plants. (It doesn't seem to root in very well at the edges, which makes it easy to pull up sections that spread too far.) I think I've seen a few seedlings, but not many.

Geranium x cantabrigiense has more of a uniform, rounded growth pattern than G. sanguineum, but it spreads more slowly. It also tends to look more stressed by our heat and humidity in late summer, but in years past, I've seen that it recovers as temps cool off and it tends to develop some lovely autumn coloration. I've also found it easy to take divisions from these plants, and I think I'll take a few more divisions this autumn and trial them in some shadier spots.

Here's a skipper butterfly on some rose verbena (Glandularia canadensis) flowers.

It's also worth considering clumping herbaceous perennials that reseed (or can be propagated by scattering or burying seeds in your garden). Plants like Agastache foeniculum (anise hyssop), Echinacea (coneflower) species or perhaps Heliopsis helianthoides (false sunflower) can block weeds, support wildlife, look beautiful and function en masse as groundcovers. Even some of the Baptisia (false indigo) species might fit that bill.

This bushy coneflower occupies space, shelters the soil and blocks weeds.

Here's a whole patch of self-sown coneflowers that function collectively as a tall groundcover. In some ways, I think there's something more appealing about this sort of groundcover than a uniform, ground-hugging Ajuga. And if you want to make room for some other plants, it's much easier to grab some coneflowers by their tall stems and dig them up than it is to try to rip out a section of an Ajuga mat.

Self-sowing perennials like Agastache foeniculum (anise hyssop) growing close together can block out many weeds.

Three false sunflowers (Heliopsis helianthoides) have grown together into one cheerful, sunny mass planting! Are there any weeds under there? Beats me. If I can't see them, I don't need to pull them! ;-)

Bushy perennials like Aralia racemosa can shade out and block many weeds. Unlike a shrub, there's no worry about pruning this plant to keep it in check. Come autumn, the thin stems of Aralia racemosa will collapse and quickly decompose back into the soil.

Some milkweeds have an upright growth habit, but this particular species (Asclepias viridis) seems to have more of a groundcover habit.

Not many weeds growing beneath this bushy Baptisia australis

This bushy blue mistflower (Conoclinium coelestinum) has not spread much yet, but it has a reputation that makes me think it could work as a groundcover. So far, it hasn't even flowered and yet I like it quite a bit anyway. The dark foliage seems dense enough to block any weeds and it seems like the perfect height - not so tall that it would compete with most bushes, but tall enough both to block weeds and to give me a good grip if I want to pull or cut any errant stems.

Native narrowleaf mountain mint (Pycnanthemum tenuifolium) also seems to do an excellent job of blocking weeds in its immediate vicinity.

Pay not attention to the geranium in the foreground. What I'm trying to show here are those ground-hugging rosettes of foliage lurking beneath the oakleaf hydrangea in the background. That's Erigeron pulchellus (Robin's plantain), and it actually seems to make a great semi-evergreen native groundcover.

Don't see any weeds beneath the 'canopy' of this perennial native senna (Senna marilandica)

The broad foliage of Solidago sphacelata 'Golden Fleece' does an excellent job of blocking weeds. (Of course, as the small spurge plant in the foreground indicates, even nearby uncovered soil is fair game for weeds.)

In sun or shade, aromatic aster (Symphyotrichum oblongifolium) makes a sense and bushy perennial groundcover, especially if the growing tips are cut back in early summer. I don't think aromatic aster spreads from the roots, but it does seem prone to self-sowing, which could help it cover quite a bit of ground over time. UPDATE 4/17 - Ended up pulling these too. As you can see, they're pretty wild looking most of the year. The autumn flowers are spectacular, but don't last all that long - maybe a few weeks? They're not very appealing in winter, a pain to cut back and they self-sow a bit too enthusiastically.

As you can tell, I'm still rolling groundcover ideas around in my head - and probably will continue to do so in the years ahead.

I apologize for the lengthy ramblings and would love to hear your thoughts on the matter! 

If you were planning to start a new, large garden bed, how would you plan short-term and long-term to keep down the weeds? 

Do you see mulch as a viable long-term choice or a short-term stopgap? 

If you were looking for an alternative to mulch, would you rely on trees, shrubs, clumping perennials, groundcover-type perennials or self-sowing annuals to fill in the space and outcompete (at least some) weeds?

The Best Groundcovers for Tennessee (so far)

The 'Grey Owl' cultivar of Juniperus virginiana (eastern redcedar) grows as a woody groundcover

It seems to me that there are two basic ways to approach gardening - you can fight against Nature or you can try to form an alliance with Nature.

When it comes to preventing your garden beds from getting overgrown by weeds, the fighting approach calls for annual (or more frequent) applications of mulch, plus annual (or more frequent) applications of herbicide.

This fighting approach seems not only wasteful from an economic and resource standpoint, but also so much effort! And not one-time effort, but constant and unending work.

The alliance approach calls for using some other plant - a groundcover - that can block and suppress the weeds for you while you sit back on your porch and drink a Mai Tai (or an iced tea, for those of the teetotaler persuasion).

Of course, it's not quite as simple as all that.

Sometimes you think you have an alliance with the groundcover, but the groundcover is actually secretly plotting world domination (or at least the domination of your garden beds).

Sometimes your ally proves too timid and weak to stand up to the onslaught of weeds or the indignities of heat, cold, wind, wet and drought that Nature throws its way.

After nearly 5 years of experiments, here are my thoughts on some of the groundcovers I have trialed in my USDA zone 6/7 clay soil Tennessee garden:

Woody groundcovers

Juniperus virginiana 'Grey Owl' loaded with 'berries' (actually berry-like cones)

Juniperus virginiana, eastern redcedar - Both the straight species and many of the J. virginiana cultivars are upright evergreen trees, but the 'Grey Owl' cultivar forms a lovely blue-grey spreading shrub.

After many years, 'Grey Owl' could grow into a large shrub - say 6 or 8 feet tall - at which point it would no longer fit a groundcover definition, though I'm interested to see whether judicious pruning could prevent or at least delay that transition from groundcover to mounding shrub.

The two 'Grey Owl' shrubs in my garden have been fantastic performers so far. They have lots of berry-like cones in the winter that are both ornamentally appealing and theoretically provide food for the birds.

The species is native throughout Eastern and Central North America and seems extremely adaptable and tough. Its only serious enemy in my garden has been the bagworm, although actually this pest has not yet appeared on the 'Grey Owl' plants, but only on some of the upright eastern redcedars around my property. Hand-picking bagworms off a 15-foot tall upright juniper is impractical, but the task should be easier if the bagworms show up on a low-growing 'Grey Owl.' And since bagworms have only one generation per year, the task is not interminable. In any case, I plan to try to combat the bagworms next year with Bt and asters, since I read someplace that asters attract beneficial insects that prey on the bagworms.

Rhus aromatica foliage, August 2015

Rhus aromatica, fragrant sumac - Again, the straight species of this plant is definitely not a groundcover, but rather a vigorous shrub that reportedly can grow 8 to 10 feet tall with 5 years.

As with the 'Grey Owl' juniper, there is a fragrant sumac cultivar called 'Gro-Low' that is much more amenable to usage as a woody groundcover. Gro-Low tends to grow outward much more than upward, forming a spreading, sprawling shrub that could make a tall base layer underneath trees.

I have mixed feelings about fragrant sumac. It has interesting cone-shaped flowerbuds in winter. Its yellow springtime flowers seem highly attractive to little pollinators. The species is a native shrub. It has red berries that provide food for birds, interesting tripartite foliage and excellent fall color. What's not to like?

Well, for starters, it's a bit rough/messy looking. Nothing wrong with that per se, but let's just say it does not have a refined or formal look to it.

It also grows so vigorously that it can be a little tough to keep in bounds (although this could be a real asset if you have a lot of ground to cover).

I've also had some problems with certain branches dying off. I'm worried that it could be a fungal disease called verticillium wilt. Perhaps the problem is that it is growing on very heavy clay soil? I've read that it prefers sandy or loamy soils and can be short-lived on clay.

Also, since this is a deciduous shrub, you will be looking at bare branches and bare ground beneath those branches for around 5-6 months in Middle Tennessee. Although the shrub has a dense growth habit that does a good job of blocking weeds during the growing season, I have seen some weeds beneath the shrub now that the leaves have fallen and uprooting those weeds without damaging the shrub itself can be a little challenging.

Cephalotaxus harringtonia 'Prostrata', Japanese plum yew

Cephalotaxus harringtonia, Japanese plum yew - This is a non-native alternative to to the 'Grey Owl' juniper. I believe the straight species of Japanese plum yew is a large, bushy plant, but the 'Prostrata' cultivar grows as a low, spreading shrub.

I've had some issues with Japanese plum yew. I had an upright ('Fastigiata') cultivar that totally failed to thrive and was soon removed (something similar seemed to happen to a 'Fastigiata' specimen growing at our local botanic garden), but the two 'Prostrata' specimens in my garden have performed fairly well in a partial shade setting. Groundcovers for the South says, "Plum yews are slow to establish and require careful attention for about two years. Once established, however, they are relatively drought tolerant and carefree."

Unlike junipers, plum yews reportedly respond well to shearing, and I've heard they can even spring back from rejuvenation pruning. Japanese plum yew is a dioecious species (meaning that plants are either male or female).

 I don't know if 'Prostrata' is a male or female cultivar, but since it's the only cultivar I have at the moment, I don't anticipate getting fruit. The sources I have seen disagree on whether Japanese plum yew fruits are poisonous. (The seeds, branches and leaves of true yews - Taxus spp. - reportedly are very poisonous.)



Groundcover vines

I've just begun to experiment with using vines as groundcovers.

Virginia creeper foliage in August 2015

Virginia creeper foliage in November 2015

In several places where native Virginia creeper (Parthenocissus quinquefolia) has sprung up in the garden beds, I'm letting it grow to see if I can manage it as a deciduous groundcover. These are early days (I used to pull the Virginia creeper seedlings until this past year) so none of these vines have covered much ground yet, but I should have more information by next year. Although it is deciduous, the vine seems to catch blowing leaves in autumn, which gives me hope that these leaves would provide enough of a groundcover to prevent germination/growth of some weeds.

Lonicera sempervirens (coral honeysuckle), summer 2013

I also plan to experiment next year with growing our native coral honeysuckle (Lonicera sempervirens) as a shrubby groundcover. I currently grow coral honeysuckle on one of my porch railings, which it forms a semi-evergreen vine that flowers for many months at a time and attracts hummingbirds in the summer. It seems incredibly resilient in terms of bouncing back from frequent hard prunings, so I have high hopes that it would make a good groundcover. (Of course, I'd have to keep a close watch on it to make sure that it did not overwhelm other plants in the bed with its vining/climbing tendencies!)

I haven't tried it yet, but I'm also considering experimenting with growing Decumaria barbara (climbing hydrangea, wood vamp) as a vining deciduous groundcover...


Herbaceous groundcovers

This is probably the biggest category, although it can be subdivided further in several ways - there are groundcovers that creep or run by herbaceous means (stolons or rhizomes) and there are those that cover ground by reseeding. I suppose one could theoretically imagine an annual herbecous groundcover - I've experimented this winter with sowing the native annual plains coreopsis (Coreopsis tinctoria) in the hopes it will fill in gaps throughout the garden, but I tend to believe the best herbaceous groundcovers will be perennials.

What characteristics should a good perennial groundcover have?

- It should have a spreading rather than an upright character. This is fairly obvious. Even though I like plants like Hibiscus moscheutos (swamp rose mallow) and Platycodon grandiflorus (balloon flower), they have a clumping upright growth habit that does not say 'groundcover' to me.

- It should multiply and cover ground in some way! Amsonia tabernaemontana (eastern blue star) has proven to be a tough perennial with a spreading growth habit. It thus meets the first criteria mentioned above, but it dies back to the ground every winter, leaving no obvious presence and must start anew in the spring. As it reaches its mature size (reportedly 3 feet wide), it might cover a good amount of ground from late spring to early fall, but I don't think it fits the definition of an ideal groundcover. In other words, I think it leaves plenty of bare spaces for weeds to get established.

- It should not be too rampant. This is a tricky one and the acceptable threshold will differ for every gardener. I approach this on a case by case basis, but I do have a few guidelines that help me determine whether something is too rampant or aggressive for my garden. I'm willing to cut the natives more slack with the understanding that they were here first, they probably have some beneficial impact on the local ecosystem and in a worst case scenario, if they get wildly out of control, I probably won't be doing any irreparable damage to the environment. It may sound silly and grandiose to think in these terms, but I don't want to be the gardener who unleashes the next kudzu on Middle Tennessee, so I exercise an abundance of caution. I'm particularly wary of groundcovers that spread secretively underground. So plants like blue star creeper, creeping raspberry and more recently hardy blue plumbago all got the boot.

- It should look good, ideally year-round or close to year-round. OK, this is a tough one. When the temperature is 10 degrees or lower - sometimes much sooner - most groundcovers start to look a bit rough around the edges. And yet...there is clearly a continuum in aesthetic appeal. Again, most of the groundcovers that I evicted were ones that added insult to injury by being both aggressive and unappealing in winter. Blue star creeper basically browned and disappeared in the wintertime. Creeping raspberry was even worse - with tough dead stems and leaves persisting for months. I waited until late spring to see if the existing creeping raspberry stems would push new foliage after a hard winter. When they didn't, I had to cut back all that dead growth so that new foliage could emerge unhindered from below ground. The hardy blue plumbago was totally herbaceous, so it disappeared below ground and left its dead bare stems standing for months.

- It should be easy to uproot. Again, I think this is especially important when we're talking about exotic, potentially invasive plants. But really, I think this is a desirable trait in any groundcover. There will be times when a groundcover gets too close to some other plant and you want to uproot pieces of the groundcover to keep a space buffer. There will be times when a groundcover has done its job, but now you have the time, money or opportunity to replace that groundcover with a shrub or tree. Once again, all of the groundcovers I came to dislike were ones that had a thick web of underground roots that made them difficult to dislodge - blue star creeper, creeping raspberry and hardy blue plumbago all fall into this category. So does buffalo grass for that matter. By contrast, desirable groundcovers such as lambs ear, perennial geranium and even (to some extent) Ajuga have proven much easier to uproot and/or relocate.

- It should ideally have some sort of ecosystem benefit beyond covering ground. Almost any groundcover plant has environmental benefits simply by eliminating all the costs associated with producing, packaging and transporting mulch and/or herbicide, but I look even more favorably on groundcovers that offer additional ecosystem benefits - e.g., flowers for pollinators, fruits for wildlife (or people) and/or foliage that can host Lepidoptera or nourish insects (that in turn provide food for birds and other predators).

I'm still testing a number of herbaceous groundcovers, but these are the ones I can recommend so far...

Stachys byzantina 'Helene von Stein', October 2013

Stachys byzantina, lamb's ear -

UPDATE - I ended up removing lamb's ear from the garden. It looked beautiful from spring to autumn, but just awful in the winter. The dead foliage was persistent, so that after a while, even the fresh new foliage was growing on a mound of dead and decaying gunk underneath. In addition to the cultivar, I got the straight species, which spread much faster and had lovely flowers with a long bloom season that attracted lots of bumble bees. Unfortunately, the flowers led to a plethora of seedlings in the immediate vicinity of the mother plant. If the old foliage decayed completely over the winter and/or if the plant didn't spread so quickly, I might have kept it. It's rock solid in the heat and didn't seem to have too many problems with our humidity. But I just couldn't deal with the old foliage and its spreading ways. Plus it's a non-native. Plus I didn't like the scent of the crushed foliage when I did try to clean it up at the end of the winter. Yuck. So... I had to give it the heave-ho.

This perennial has a lot going for it. First of all, it's adorable. The fuzzy leaves will make you want to rub them every time you walk by. I love the grey-green foliage that grows thickly enough to block just about every weed.

Lamb's ear reportedly dislikes humidity, but the 'Helene von Stein' and 'Fuzzy Wuzzy' cultivars have stood up very well through several typically hot and humid summers.

It's true that lamb's ear will basically collapse and disintegrate during a very cold winter. Although I should point out that all the lamb's ears look great this year into December. The winter has been very warm so far, but we have had several nights below freezing and the lamb's ears all seem unperturbed.

The cultivars I have don't flower much, but I did get one flower stalk this past year and it flowered for a long time with blooms that attracted pollinators, so that's an added bonus in my mind.

The plants expand very fast - Fuzzy Wuzzy in particular seems to have grown about 2-3 feet wide in a single year - and yet I have found that they are easy to uproot if you find they are growing too big for their space.

That said, I do have a couple of concerns:

First, although they are easy to uproot, they are not necessarily easy to divide. They grow so thickly that when I tried to divide the too-big-for-its-space lamb's ear, I ended up making such a mess that I just decided to shovel prune the whole plant. This was in early autumn, so I intend to dry division on another plant this coming spring. Perhaps when I rake aside the old leaves and spot the new ones emerging from the soil, I'll have an easier time making the division? I'll report back on the results of this experiment.

Also, I'm a little concerned that the plant grows so thickly that it could block water from reaching the roots of trees and shrubs. In the past, I've simply allowed the old leaves to remain on the ground, but I think I can alleviate this concern and probably improve water penetration by raking the old leaves out of the way. Again, I'll report back after I give that a try.

It's a non-native, but lamb's ear has not seemed aggressive in my garden. I am not aware of it appearing on any invasive lists in the U.S. (For instance, Washington State University Clark County Extension recommends it as "a nice spreading groundcover that does not become invasive.")

I also have to give it extra points for the way it seems impervious to damage by rabbits or deer. Lamb's ear has grown well in my garden in both full sun and partial shade, although it will grow faster in full sun.

Geranium sanguineum, bloody cranesbill, 'New Hampshire', July 2013

Geranium x cantabrigiense, Cambridge geranium, 'Biokovo', still evergreen in March 2015 after a harsh winter

Geranium species - The cranesbill geraniums are some of my favorite groundcovers. In fact, they are some of my favorite perennials overall.

I especially like G. sanguineum (bloody cranesbill) and G. x cantabrigiense (Cambridge geranium), both of which seem to be vigorous, floriferous and beautiful groundcovers for partial shade. They both stay more-or-less evergreen during the winter months, spread at a healthy though manageable pace and do a good job of blocking weeds. It seems easy to control the spread of these geraniums by slicing off pieces of the plant from the edges of the clump. And unlike the lamb's ear, I've been able to successfully transplant portions of the clump elsewhere in the garden. The aromatic foliage not only smells great, it also seems to repel rabbits and deer.

Although these are non-native plants, they do not show any indication of reseeding or behaving invasively. (I believe some other species or cultivars of cranesbill geraniums may reseed, but I don't know that even those are considered invasive.)

Both species also flower for a good number of weeks in the early summer and bloody cranesbill in particular can have a bit of a rebloom in autumn.

If you're looking for nonstop flowering for months, it's hard to beat the 'Rozanne' cranesbill geranium. Just be aware that Rozanne will go deciduous in a cold-winter climate. In my experience, Rozanne has been shorter-lived than the other species.

Ajuga genevensis, Geneva bugleweed, flowering and spreading in April 2014

Overhead view of Ajuga genevensis, September 2013

Ajuga spp., bugleweed - Sadly, none of the bugleweed species are native to the U.S. (as far as I know), but I do think several of them deserve consideration as garden groundcovers. The most common species you'll find at nurseries is A. reptans, but I think I prefer two harder-to-find species - A. genevensis (Geneva bugleweed) and A. tenorii (Tenore's bugle ... most often available as the 'Chocolate Chip' cultivar). In general, the bugleweeds have a lot going for them. Here in zone 6/7, they're pretty well evergreen. Their old foliage may get beaten up in a harsh winter, but it still does a good job of covering the ground and blocking weeds.

Unlike some groundcovers (lamb's ear, for instance) which seem to get a bit thicker each year as they mound on top of old foliage, bugleweed seems to stay very low to the ground. I guess the old leaves decompose pretty thoroughly each winter? Or maybe I just haven't grown it long enough and it will start mounding at some point in the future.

I find A. reptans a bit ... unpredictable. In my experience, it sometimes dies out for no apparent reason (I'm guessing fungal issues), or parts of a patch may die out while other parts thrive. If it dies out in the middle and you leave it along, it may fill in again with time.

Ajuga genevensis has been a more sturdy, reliable performer so far. It spreads methodically and predictably at a measured pace, neither leaving gaps nor racing ahead. I've had excellent success chopping off pieces at the edges of an A. genevensis patch and transplanting them elsewhere in the garden. Geneva bugleweed seems to thrive in partial shade, but I have some patches that get plenty of sun and they have proven themselves very drought tolerant on clay soil. (I can't say if they'd be drought tolerant in sandier conditions.)

If you're worried about Ajuga spreading too quickly, I'd recommend A. tenorii. Tenore's bugleweed has much slimmer leaves than the two other species and seems to have more of a clumping habit. It seems like the clumps get larger with time, but (so far) at a slower pace than either A. genevensis or A. reptans.

I must admit that some states (such as North Carolina) list A. reptans as an invasive plant, so that does give me pause. Although North Carolina only lists bugleweed as a Level 3 invasive - meaning one that only seems to spread into disturbed areas and does not appear to pose a threat to native plant communities. In a few years of growing bugleweed, I think I might just be starting to see a few seedlings here and there, but mostly it has spread by vegetative means.

In terms of ecological benefits, all the bugleweeds have spikes of blue or purple flowers in the spring that seem quite attractive to bumblebees.

Coreopsis verticillata, threadleaf coreopsis, 'Zagreb', June 2015
(2nd year in the garden, starting from two 4-inch pots planted in April 2014)

Coreopsis verticillata, threadleaf coreopsis, 'Zagreb' - A native of the Southeastern U.S., threadleaf coreopsis has been a great garden plant for me so far. In partial shade, the 'Zagreb' cultivar has bloomed pretty nicely with pretty yellow flowers that attract small pollinators. Threadleaf coreopsis forms clumps that expand outward at a measured pace. I have not tried dividing or transplanting any pieces of these clumps yet, so I can't say how easy it is to divide or remove it. In any case, since this is native to the region (though not really to Tennessee), I feel a bit better about using it in the garden.

In my garden, the clumps have grown perhaps 10 or 12 inches tall and seem to do an excellent job of blocking weeds. It is an herbaceous plant, but the stems grow so closely together that the dead stems still protect the soil and block weeds during the winter. I like this plant so much that I went out and bought about 9 more specimens this autumn and planted them in various places in the garden. I'm trialing it in some much sunnier spots and I hope that it will thrive all around the garden.

Echinacea purpurea, purple coneflower, June 2015

Echinacea species, coneflowers - This may seem like a little bit of an odd choice. Neither purple coneflower (Echinacea purpurea) nor Tennessee coneflower (E. tennesseensis) is marketed as a groundcover, but I think in practice it can form a decent groundcover beneath trees or shrubs that have been limbed up.

I don't think coneflowers spread by rhizomes, but as the plants get older, the clumps get bigger and the large basal leaves do a good job of covering ground for much of the year. Just as importantly, if you leave the seedheads standing over the winter for the birds, a number of those seeds will fall to the ground and germinate and pretty soon you'll have a large patch of coneflowers. As the coneflowers cluster thickly together, they will block many weeds. You can help this self-sowing process along by cutting off some of the seedheads and burying the whole head in the ground. After a few years, I had so many purple coneflowers that I actually thinned out the patch quite a bit this autumn to give me space in the garden beds to trial some other plants (such as asters and goldenrods).

I'm sure there are some other self-sowing annuals or perennials that could work the same as coneflowers, but nothing comes to mind at the moment. I do grow some self-sowing annuals - Cosmos bipinnatus and Tagetes patula (French marigold), for instance - but neither one of them seems like a great groundcover candidate, at least not here in Tennessee.

Cosmos has such a narrow presence in the garden (i.e., no basal leaves to speak of) that even a mass of cosmos won't necessarily block weeds at their base.

Tagetes patula can block weeds in its immediate vicinity, but I don't find that it self-sows particularly reliably here. Even after harvesting and scattering seeds all about the garden last winter, I think I only had 5 to 10 new French marigold plants this spring. And only one of those French marigolds got bushy enough this year to do a good job blocking weeds within a 1 foot radius. The others all stayed petite and sparse.

If you go for an annual that self-sows more rampantly - such as love-in-a-mist (Nigella damascena) fits that bill for me - you may find yourself picking out hundreds of extra seedlings from the beds, the lawn, cracks in the sidewalk, etc.

No, I think what you really want is a self-sowing perennial -- one that doesn't inundate you with seedlings, but gives you perhaps a few dozen new plants in a year, with each of those plants living for at least a few years and having significant enough basal foliage to shade the soil.

Gaillardia x grandiflora (blanket flower) could fit the bill. The individual plants have a reputation for being short-lived, but the basal foliage is certainly rather thick and persistent in winter (even more so than purple coneflowers) and I feel like mine have been gently self-sowing. I don't get nearly as many volunteers as with the purple coneflowers, but my Gaillardia patch has been slowly multiplying in size. Perhaps that's even better? After all, if you only have a few new seedlings per year, you won't have to weed out as many unwanted extra volunteers.

Oh I should mention that all the Echinacea species I've tried - especially E. purpurea - seem to be a big hit with bees (especially bumblebees), butterflies and birds. The blanket flowers also attract pollinators.

Epimedium x perralchicum 'Frohnleiten', May 2015 - love that colorful new foliage!!

Epimedium x perralchicum 'Frohnleiten' - The Epimedium species have many interesting common names such as fairy wings, bishop's hat, horny goat weed and barrenwort. These non-native plants are not especially flashy much of the year, but they do have a reputation for being dependable evergreen or semi-evergreen groundcovers.

There are lots of species and hybirds out there. I've grown Epimedium x perralchicum 'Frohnleiten' for a few years now and I can say that while it took a while to settle in at first, it has since become a very dependable, handsome and carefree groundcover for partial to full shade. It expands at a very manageable (some would say 'slow') rate, so it's unlikely to run over any other plants before you'd notice. I think the foliage is gorgeous and the flowers are very interesting (though I seem to recall that they were rather short-lived and I don't recall whether I saw any pollinators visiting them).

People say that you should cut or crumble the old foliage (which will be pretty brittle) at the end of winter to make way for the new leaves to pop up. I'm not sure that's actually necessary (after all, no one crumbles the old foliage for Epimedium plants growing in the wild!) so I may try letting the old foliage decompose on its own this year just to see if there's any noticeable aesthetic difference.

I was so pleased with Frohnleiten that I'm now experimenting with two other kinds of Epimedium - E. versicolor 'Sulphureum' and E. warleyense 'Orange Queen'

OK, this is not exactly a beauty shot, but this is the way that Erigeron pulchellus var. pulchellus 'Lynnhaven Carpet' looks in mid-December. It may not win any beauty contests at this point in the year, but I would like to point out that it's still doing a decent job of covering ground and I don't see any weeds popping up in its midst. Still, this has been an unusually mild winter (only a couple of nights in the 20s so far). It will be interesting to see if it continues to protect the soil and act as an evergreen groundcover if temperatures fall into the teens or single digits.

Erigeron pulchellus var. pulchellus, Robin's plantain, rose petty - 'Lynnhaven Carpet' - Although Erigeron pulchellus is native to Tennessee and across much of the Eastern and Central U.S., I don't think I'd ever heard of it until recently. That's really a pity, because although this species can be a bit shy and modest, I think it makes a very interesting groundcover for partial to full shade. The grey-green basal foliage of my 'Lynnhaven Carpet' specimen grows very low to the ground - rather like Ajuga, but perhaps hugging the ground even tighter.

In the spring, it sends up airy stalks of lavender flowers that fade to white as they open. Those flowers may attract small pollinators.

After the flowers fade, Robin's plantain fades into the background, but its evergreen leaves do a good job of blocking weeds and I like the way it has spread at a measured pace. In about 18 months, a single small plant has spread into a patch of rosettes perhaps 12 or 18 inches across.

I liked this plant so much that I purchased three more quarts that I'm trialing in various places around the garden to test their tolerance for different levels of sun exposure. The specimen of rose petty that has done well in my garden grows in partial (morning) sun, but I'd say it actually gets mostly shade since it is swamped during the growing season by a 'Rozanne' cranesbill geranium and further shaded by an oakleaf hydrangea growing nearby. When both of those plants drop their leaves in autumn, Robin's plantain reveals herself standing strong, just waiting for her moment in the sun.

Teucrium chamaedrys, wall germander, August 2015

Teucrium chamaedrys, wall germander - 'Prostratum' - Another non-native (sad to say) but one that has proven to be a strong groundcover in my garden. I think I have the 'Prostratum' cultivar that tops out at around 6 inches tall and spreads by underground rhizomes.

Now generally I'm not all that happy when plants (even groundcovers) start spreading underground and popping up in unexpected, non-contiguous locations. I wasn't happy when blue star creeper did that. I wasn't happy when hardy blue plumbago did it either. So why am I willing to cut wall germander some slack when it behaves in a similar fashion?

First of all, it doesn't seem to spread very far underground. I'd guesstimate that most of the new shoots pop up within 4 inches or less of the main clump. That's not too bad.

Secondly, it seems quite easy to uproot any sections of germander that creep too far. In fact, I dug up quite a bit of the clump this fall and transplanted three different plugs to different parts of the garden to see how this will fare with different sun exposures.

I also like the fact that it is more-or-less evergreen (at least semi-evergreen) in Tennessee, so it looks good (and blocks weeds) all year long.

Three small plugs of germander have grown together quite nicely into one decent size contiguous patch over the past 18 months. The stems in this clump seem to do a good job of catching fallen leaves, which I hope means that the plant will improve the soil as the leaves decompose. (The other possibility is that the plant will be smothered by all those trapped leaves.)

Teucrium chamaedrys also has nice long-lasting pale purple flower spikes that attract bees during the summer. I cut off the flower spikes when they were done blooming, but I think I should have trimmed the old stems to the ground. Instead, I cut off the spikes, but left the old stems standing. As a result, I have some bare stems with a bit of new growth on the top.

Next year, I'll try chopping the whole plant near the ground after the flowers fade and will report back on whether it invigorates or hurts the plant.

*****

It probably goes without saying, but YMMV (Your Mileage May Vary).

If you live in a much colder, hotter, drier or wetter zone, none of these recommendations may work for you. If you're in another state or another country, my native and non-native distinctions could be irrelevant or even reversed. But I hope my personal experiences may help you or at least give you inspiration to find the ideal groundcovers for your garden :)

PS - I'm continuing to trial a number of new plants. I've added some to the garden this autumn and plan to add more in the Spring! Some of these newcomers will be groundcovers. I plan to introduce all the newcomers throughout 2016 and then report back eventually on how those new additions actually perform in the Garden of Aaron!


What are some of your favorite groundcovers? 

Have you had good (or not-so-good) experiences with any of the plants I've highlighted above?

Or did I miss a groundcover that works especially well for you?