Cracked!

Mind the gap!

Just a pic to illustrate the challenge of gardening on compacted Tennessee clay 'soil' (subsoil?)

It looks from this image like we hadn't had any rain in months.

But this is just what my soil looks like if we go a couple weeks with warm weather and not much rain.

(This pic was taken about a couple weeks ago. At the moment, much of the back yard looks like a shallow pond since we've had several days of hard rain with flood warnings across the area. But next time we have a couple weeks of dry weather, it will go right back to this cracked look.)

Could I amend the heck out of it? Sure, but it would be back-breaking, soul-crushing, expensive, time-consuming and ecologically-questionable.

Instead, I try to find ultra-tough plants - many of them natives - capable of surviving and even thriving in this pottery material.

Ultimately, where the plants thrive, I find that the soil does improve over time. Slowly. In a few hundred years of letting Nature work its magic, I might have some nice loam! 😉

Evidence of Poor Drainage

A photo is worth 1000 words:

More than 12 hours after a heavy rainfall...

Digging a hole and filling it with water to check how quickly the soil drains is considered a standard way to check whether you have soil compact and poor soil drainage.

I didn't intentionally dig this hole to check soil drainage. I dug it in the process or removing an Euonymous alata (a.k.a. Burning Bush), which is listed by the National Park Service as an invasive plant.

I haven't quite gotten around to figuring out what I want to plant there, but whatever it is, it had better be comfortable with periodic flooding.

I already knew the soil drainage was not great in large parts of the backyard. The yard is sloped downward toward the street in the front, so the drainage is better there, but after heavy rains, parts of the back yard can stay soggy for days. When I hired a landscaper to add some plants to the back yard this year, he showed me just how compacted and dense the soil is back there.

I believe that the problem, as in many relatively new developments, has to do with soil compaction caused by heavy machinery. Plus I imagine that the top soil may have been scraped away to sell early in the construction process, with only a thin layer of soil (probably attached to the grass sod) put down when construction was complete. I can tell you there's about a half-inch of black soil attached to the grass in the backyard and then it's heavy, sticky, thick, murderous clay as far down as you can dig.

Thus the subtitle of this blog - Adventures in Gardening on Tennessee Clay!

That being said, the drainage is not equally bad everywhere in the backyard. Perhaps 30 feet away from the hole above, I dug another hole (while removing another burning bush). As you can see below, that hole did not hold water for nearly as long after the same storms had rolled through.

Not nearly as much water in this hole, although quite a bit of mulch has washed in

So what's the problem with poor drainage? Roots need water, but they also need oxygen. Yes, roots need to breathe! If soil stays saturated for lengths of time, roots can drown and/or rot.

There are plants that can survive in wet or continuously moist soil, but they are not usually the same plants that are able to survive drought, which is also a regular occurrence in Tennessee.

Similarly, many drought-tolerant plants require well-drained, sandy or rocky low-fertility soils, which are clearly not the prevalent conditions here.

I'm compiling a list of plants that can survive both drought and flooding (plus single-digit winter lows and above-100 summertime highs). For instance, Baptisia australis (False Indigo) reportedly can withstand both severe drought and extended flooding.

I'd love to have suggestions to add to the list!

Buffalo Grass Trial - Day #2

Buffalo grass plugs newly installed, Day #2, August 23, 2012

Yesterday, my mail order of Prestige buffalograss arrived from Todd Valley Farms.

(Yes, this is the same Todd Valley Farms referenced in my interview with Wayne Thorson about the virtues of buffalograss. In case you're wondering, I did not get any perks or discounts from Wayne or Todd Valley Farms in exchange for the interview. You can read the Trust section of this website if you'd like to learn more about my policies and promises on editorial integrity. I bought my buffalo grass fair and square in a 95-plug tray for $48 plus $14 shipping and handling. I looked around and investigated buying the buffalo grass through other mail order outlets, but the ones I investigated seemed to basically just be distributors for Todd Valley Farms, so I just decided to buy from the source.)

I have to admit that I was very excited to open the box and see the thick carpet of Prestige buffalograss therein. Despite three days in transit in mid-80s to low-90s weather, the plugs looked healthy, strong and green. Yes, the grass is a softer, greyer color than fescue or bluegrass, but it was incredibly soft and all the blades were nicely interconnected in a way that seemed like it would do a good job of excluding weeds.

In fact, the stolens on the buffalograss were so interwoven that it was impossible to pull the plugs apart without cutting them. My wife graciously volunteered for this task while I set to work trying to dig holes in the rock-hard clay that we call soil.

(I'm sorry I didn't take a photo of the buffalograss looking so pretty in its tray. I was eager to get the plugs untangled and planted. As it was, the job took us ~3 hours and we only finished around sunset. It would have taken far longer without the help of my generous and kind wife!) 

Incidentally, this buffalograss test patch was installed where we previously had our raised garden bed. I disassembled the bed a few days ago, distributing some of the soil therein throughout the landscaped beds and raking the remaining soil to the point where it looked relatively smooth with a nice slight grade away from the house and patio.

Anyway, back to the digging. It was hard work, chopping at the soil with a small shovel. If I were planting more than one tray (and even if I were doing one tray again), I'd certainly consider buying some sort of auger attachment for my drill to make the work go faster and easier. Or I might try the approach my wife suggested, which would be to use a big shovel to chop up the top layer of dirt throughout the whole planting area and then plant all the plugs into that loosened soil. Or maybe it would have been better to use a tiller? I'm not sure yet and confess that I still have a lot to learn about soil!

Prestige buffalograss plugs close up after installation

In any case, we watered down the area, watered down the plugs themselves and chopped out holes in the soil. I didn't worry too much about placing the plugs at exact distances from each other, but I did try to stagger the rows as recommended in the planting instructions. (By 'stagger the rows', I mean that I wanted the post-planting area to have a checkerboard pattern.)

The planting and care instructions sent by Todd Valley Farms are rather chemical dependent. They recommend soaking the plugs with Miracle Gro®or a similar sod/seed starter fertilizer and using chemical herbicides to suppress weeds.

As an organic gardener, I basically ignored those instructions. Instead I scattered some chicken manure and earthworm castings into each of the holes and plan to spray some organic liquid fertilizer in a few weeks. As far as I can tell, the fertilizers that are recommended (every 30 days according to the planting instructions) are not absolutely essential - after all, no one was spraying buffalograss with fertilizer when it was the dominant grass on the Great Plains! - but rather just to encourage the buffalograss to fill in its area before weeds pop up to compete. Since I'm not using an herbicide - some of which like 2-4D can apparently harm the buffalograss itself - I'll need to just be vigilant about weeds and try to pull them before they get established. Since this is a compact area (probably not more than 50-60 square feet), I'm hoping I can deter the weeds until the buffalograss fills in and gets strong enough to screen them out on its own.

Update - Just called Todd Valley Farms and was told that using organic fertilizer is fine, just to try to use one that supports root growth - i.e. one that has more P and K, versus N that would encourage top growth, which would be counterproductive without the roots to support that growth.

An overhead shot of the buffalograss plugs. The slightly darker patch of soil in the middle of the photo is where I emptied out the last of the earthworm castings. I wish all my soil was that dark and rich. Yes, I have Soil Envy!

So that's where things stand for now. The instructions emphasize keeping the plugs wet for two weeks, so I soaked the area thoroughly right after planting and again this morning. I spoke with Todd Farms to ask exactly what this meant in terms of how often to water the plugs, but was told that it was impossible to give a hard answer since the watering frequency would depend on temperature, soil, etc. Basically I was told that I should keep the area 'wet' for two weeks (wet meaning you wouldn't want to walk on it) and then 'moist' for another two weeks (moist meaning you could potentially walk there). I was also given the reassuring news that the plugs are a bit less sensitive to drying out than the sod.

And while some buffalograss buyers have reported problems with their grass turning brown, again as I understand it that is more of a problem with buffalograss sod and/or with spring plantings where the grass is taken out of a warm greenhouse and plopped into a colder environment. Since it's going to be in the low 90s today and for the next couple of days, I don't think I have to worry about cold temperature shocks with the buffalograss!

Prestige buffalograss plugs and one zinnia, one of a couple plants that I didn't have the heart to remove when I was preparing the buffalograss bed

So, I'm very excited to be giving this a try! Hopefully temps will cool off in a week or so (that's the long range forecast) and we'll get some rain which will cut down on the amount of watering I need to do, but for now I'm willing to do some intensive short-term watering for the future promise of less watering down the road. As the "General Care Guidelines After Establishment" in the planting instructions state:

"You should not need to water your buffalograss except in times of drought. If this occurs, deep water (1 to 2 inches) once per month. This will keep your lawn looking lush. Adjustments to this may need to be made due to soil conditions and/or local climates. If you choose not to water, this will not harm the grass (my emphasis) but you may notice a slight browning of the blade tips. Buffalograss will go into dormancy in extreme droughts."

All of this sounds awesome to me. The promise of a lawn - or at least a patch of a lawn - that needs hardly any supplemental water and grows slowly to a maximum height of 4-6 inches tall? That is the dream I am pursuing with this buffalograss trial.

Will the buffalo grass ever knit together into a green carpet? Or will it remain as a patchwork of isolated clumps? Find out (eventually) with free email updates.

Expert Interview #2 - Kirk Shillinglaw, Prairie Nursery

Monarch butterfly and bee on Prairie Blazingstar, photo by Rachel Ford James

As I mentioned when interviewing Ira Wallace of Southern Exposure Seed Exchange, my hope with GardenofAaron.com is to share not only my own limited knowledge and experience with gardening, but also to bring you the views, opinions and wisdom from authorities in the field.

For that reason, I’m honored to be able to present an interview with Kirk Shillinglaw, VP of Sales and Marketing at Prairie Nursery. Although Kirk carries a businessperson’s title, he assured me that he was formerly seed division manager at Prairie Nursery, which means that he is well acquainted with the virtues of various prairie and native plants.

GardenofAaron.com:  Tell me what makes Prairie Nursery different from other plant nurseries and seed catalogs.

Kirk Shillinglaw: We were one of the first nurseries to use native perennials in landscaping. In fact, we just celebrated our 40^th anniversary in business, which makes us one of the oldest – if not the oldest – native plant nurseries.

In addition, we have very high quality seed and plants. All the seed we sell is lab-tested for quality and viability, and we hand-grade all our plants. 

And we have something for  just about any soil type or condition. Our annual sales reports show that we have customers in all 48 contiguous states. In the Southeast, many of our customers are located in North Carolina and Tennessee.

GardenofAaron.com: Why should gardeners consider using native plants in their landscapes?

Shillinglaw: If you choose the right plants that fit your soil and sunlight conditions, then native plants will be naturally adapted to the local conditions. Natives are generally hardy and disease-resistant plants. They often attract birds and butterflies by serving as a natural source of seed and food for pollinators. They are typically low-maintenance and many of them have good drought tolerance. While some natives do naturally experience a certain degree of insect predation, they’re generally less likely than exotic plants to get absolutely mauled by insects, which means that usually gardeners do not need to resort to insecticides to keep a plant alive and healthy.

GardenofAaron.com: Where I garden in Tennessee, the soil is mostly clay. Many other gardeners in the Southeast and elsewhere in the U.S. garden on clay soils. What sort of plants would you recommend for them?

Shillinglaw: We actually have a strong line of clay plants that we call Clay Busters. The great thing about using these plants is that you don’t have to amend the soil.

GardenofAaron.com: Really? You don’t have to amend your clay soil at all before planting these Clay Busters?

Shillinglaw: Well, we suggest removing competing vegetation to reduce some competition at the start. If you plant a native plant into a patch of quack grass, it will have a tough time getting established. So give the plants an even playing field, dig a hole, loosen the roots of the potted plant, ensure that you have some loose soil at the bottom of the hole and then tuck the plant in. You do need to give the plant some water in its first few weeks until it gets established so that it can get its roots into the soil.

GardenofAaron.com: So which of the Clay Busters would you specifically suggest for someone like myself gardening in a sunny patch of Tennessee clay?

Shillinglaw: One of the most commonly and frequently used clay plants is the Purple Coneflower (Echinacea purpurea). Another popular one is Prairie Blazingstar (Liatris pycnostachya). Those are two of the most well-known native prairie plants.

Another plant that can work well in clay is Rattlesnake Master (Eryngium yuccifolium), which has a really unusual and unique appearance.

And one of my favorites is the New England Aster (Aster novae-angliae), which in Tennessee might bloom through November.

In moist clay, Ironweed (Vernonia fasciculate) can be a good choice if you’re looking for a tall plant [4-6 feet].

Butterfly on Rattlesnake Master, photo by sfgamchick

GardenofAaron.com: You said Ironweed is good for moist clay. What if you have clay soil like mine that is moist after one of our strong rainstorms and slow to dry, but then bakes like concrete in hot, dry weather? And what if you want a plant that can take drought without a lot (if any) of supplemental water?

Shillinglaw: In that case, you want to look for plants like Yellow Coneflower (Ratibida pinnata) and Black Eyed Susan (Rudbeckia hirta) that are listed in our catalog or on our website as doing well in any kind of soil – Dry, Medium or Moist. The plants that have that description will generally be more cosmopolitan and adaptable with regards to soil moisture. Note that Black Eyed Susan is a biennial, but does self-sow on bare ground, and the vast majority of our plants are perennials that you can plant once and that will come back year after year.

GardenofAaron.com: Changing topics a little, do you grow your own plants?

Shillinglaw: We do grow approximately 95% of the potted plants we sell in our own greenhouse. Much of our seed is also produced on site.  

GardenofAaron.com: I am trying to do some of my planting in autumn this year (as opposed to this year and last year when I planted in springtime). How do you feel about autumn planting in Tennessee or elsewhere in the Southeast?

Shillinglaw: Planting in fall can be a good idea to help plants get established and put down roots so that they grow a bit more strongly next spring. While most spring transplants will still bloom their first year in the ground, you’re more likely to get blooms the following year on a fall transplant. Our autumn shipping season runs from mid-September to mid-October, although we will ship a little later to Southern areas on request. For large orders, we can sometimes make exceptions and ship outside of this time frame.

GardenofAaron.com: What are your recommendations when it comes to fertilizing native plants?

Shillinglaw: Generally, there is no need to fertilize native plants. In fact, we find that adding fertilizers may actually tip the balance in favor of competitive weeds. Of course, like anything that is green and growing, if you have a plant that is looking really poor, you might want to add a balanced fertilizer, but generally there is no need to fertilize with native plants.

GardenofAaron.com: So in the Southeast, where we have a lot of rainfall, but we alternate between periods of heavy rain and drought, would you suggest looking mainly at plants listed as tolerating dry to moist conditions?

Shillinglaw: Well, it depends on soil type. I know quite a few people garden on clay in the Southeast, but if you have a sandy soil, you’re more likely to lose moisture quickly even after a heavy rain. In that situation, plants that we have categorized as suitable for Dry, Sandy & Rocky Soils would be most suitable.

GardenofAaron.com: What plants would you recommend for shade or partial shade on clay soil?

Shillinglaw: Well, Trillium (Trillium grandiflorum) is one good option. Another good choice might be Sweet Joe Pye Weed (Eupatorium purpureum). Wild Ginger (Asarum canadense) is a tremendous groundcover for shady or partially shady areas on clay soil. Even a few of the woodland asters, like the Heart Leaved Aster (Aster cordifolious) and the Big Leaf Aster (Aster macrophyllus), can do well in clay and partial shade.

Wild Ginger (Asarum canadense), photo by gardentrek

GardenofAaron.com: Speaking of groundcovers, any suggestions in that area?

Shillinglaw: We don’t really carry any vines that would rapidly cover an area, but almost any of our ferns has the potential to spread and attain good coverage. Stiff Coreopsis (Coreopsis palmata) can also spread and function as a groundcover. And then there’s Wild Stonecrop (Sedum ternatum), which can function as a groundcover. Another good option might be Palm Sedge (Carex mukingumensis), which has unique foliage that looks like the leaves of a palm tree.

GardenofAaron.com: Would you say that interest is growing in the U.S. in native, prairie plants?

Shillinglaw: I’d say that the market for purists or traditionalists looking to restore native prairie lands has stayed about the same size in recent years, but we do have more and more customers and potential customers who realize that native plants don’t have to look wild and weedy. A lot of native, prairie plants make excellent garden plants. Very few of these natives are aggressive, which means that they will mostly play well with others.

Also, pretty much everyone likes birds and butterflies, and so the fact that these plants often do a good job of attracting that sort of wildlife is a strong point in favor of the native prairie plants. Generally, I’d say they are becoming more mainstream and more accepted by landscape designers and customers.

GardenofAaron.com: Presumably a lot of the native plants are also attractive to bees and hummingbirds?

Shillinglaw: Absolutely, bees love plants like Bergamot (Monarda fistulosa), which is commonly known as Bee Balm. And Columbine (Aquilegia Canadensis) is an excellent hummingbird plant. Our catalog and website has icons showing which plants are best for attracting birds, hummingbirds and butterflies. And next year, we’re planning to add a bee icon to highlight plants that attract pollinators. We are working on that project with the Xerxes Society, which aims to protect pollinators.

GardenofAaron.com: Anything new that we can expect from Prairie Nursery down the road?

Shillinglaw: We have been building up the woodland species that we offer, for instance by increasing our selection of woodland ferns. And we are starting to look at offering a few native shrubs, for instance plants like Elderberry. So that’s something to keep an eye on for next year.

Thanks to Kirk at Prairie Nursery for these insights!

It’s almost fall planting season at GardenofAaron.com. So stay tuned for photos and play-by-play on some of the big changes coming to the garden!

Have you ever ordered from Prairie Nursery? 

Do you have any native and/or prairie plants in your garden and, if so, how have they fared? 

Please share your experiences in the Comments field below.