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! 😉

Daikon as Clay Soil Amendment (and Tasty Vegetable)!

Daikon foliage, pre-deer (the stems coming out of the daikon at the bottom of the photo are actually from another annual - redwhisker clammyweed - that was growing in the same area where I scattered the daikon seeds)

In the U.S., when we think of radishes, many of us think of the cute little red skinned radishes.

I like those little reds as much as the next guy, but let me tell you something - they do not thrive on heavy clay. And by 'do not thrive', I mean that when I tried growing them, most of them failed to develop anything resembling the round, bulbous shape that the word 'radish' conjures. It was an abject disappointment.

But daikon radishes - sometimes known as tillage radish - is in a different category altogether. In fact, daikon radishes are so renowned for their ability to penetrate compacted clay soils that some people use them as a winter cover crop to aerate the soil (example Delta Farm Press). Note that if you're growing it to amend the soil, the idea is not to harvest the radish, but to allow it to winter kill and then decay in the soil.

Daikon foliage, post-deer (or possibly post-rabbit)

Having just removed some shrubs from a garden bed, I had some bare soil in September and no firm idea what I wanted to plant there yet. I thought I'd do a trial planting of daikon to see (a) if it could make a good cover crop and (b) if I could get any sizeable radishes from the bed for eating.

I happen to enjoy eating daikon radish, for instance sliced and added on top of a salad.

I sowed the seeds (from Sow True Seeds) in September, gave them a couple drinks of water to get started and then basically left them alone to fend for themselves during two months of severe drought that followed.

How did they fare?

Color me impressed. As a cover crop, daikon produced a nice head of leaves that sheltered the soil and blocked weeds. (The leaves are also edible, fyi.)

And the roots actually did manage to penetrate the hard-as-concrete parched clay soil. In fact, the soil was so tight that I had to water the plants just to pull some of the radishes without having them break in the middle.

A couple of daikon radishes pulled from the concrete, er... clay, soil

Now, it's true that my radishes did not reach the mammoth portions of ones grown in sandy-loamy soils. In Japan, where daikon radishes are quite popular, the roots can easily be 12 inches long with the diameter of a baseball bat. My daikons were only about one-third that size, but consider their growing environment and the lack of rain (which would probably have softened the soil and allowed the daikon root to expand deeper and wider), I was quite impressed and pleased with their performance.

How was the taste? I was expecting that the lack of rain would have made the radishes hot and spicy, and indeed the first daikon I ate was almost too hot to handle, but the subsequent ones I consumed generally had just enough bite.

Sliced daikon makes a lovely salad topping

I did run into two problems - deer and rabbits.

The daikon leaves seemed mainly untouched in late October, but throughout November, I saw more and more herbivore damage (and telltale deer droppings scattered around the backyard pointed to the culprits). I figured the deer shouldered all the blame, but late in November, I spotted a well-fed bunny scampering from the radish patch, so I'm dividing the blame among both types of critters.

Still, I can't blame them too much. A nearby wood has been mostly clear-cut this summer, and the drought meant that much surviving wild vegetation was parched, dead or dormant. Finding this green salad bar in my backyard probably seemed like quite a treat - maybe even a life-saving one - for the critters.

I saved some seed and hope to try again in the spring. If we have normal rainfall this winter (the last week has been promising), hopefully there will be plenty of other wild greens for the local herbivores to eat and I'll get a chance to see how the daikon fare without being denuded of their foliage. (Neither the rabbits nor the deer touched the radish root, so technically I could still dig up and eat some of the daikons, but I think I'll let them decompose over the winter to help the soil.)

Overall, I'd say this experiment was quite fun, tasty and successful. So much so, that I plan to grow a lot more daikon in the future. And for any other gardeners out there stuck with heavy compacted clay - consider giving daikon radishes a try!

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.