By Jill Henderson – Show Me Oz –
The first few months of addressing the severe erosion on the terraces cut into the hillside behind our house involved a lot of physical labor. With shovel, rake and clay-covered boots, we were able to repair the worst of the damage and redirect the runoff into the adjoining swale. But that was just the beginning. Once the repairs had been made, we had to figure out just how we were going to stabilize the barren expanse of clay and rock hovering a mere 20’ from our back door. The first and most obvious answer to permanently stabilizing the terraces was to vegetate them. Doing so might seem elementary, but as anyone who has ever lived in an area with clay “soils” knows that getting anything at all to grow on a mountain of solid red Ozark clay and rock is easier said than done – even for a pair of skilled gardeners like Dean and I.
Before we began this second phase, I decided to learn more about clay soils. The first thing I found out was that clay is not considered “soil” at all. Indeed, clay is actually a type of mineral deposit that consists of spherical granules, which are smaller and finer than those of silt. Some clays are formed through the dissolution of silicate based rocks, such as limestone, while others are deposits laid down on the bottoms of shallow lakes and seas.
For millions of years, the Ozarks were little more than a reef-flanked chain of islands in the warm, shallow waters of a Paleozoic sea. Over millions of years, the entire area was submerged, uplifted and submerged again. The repeated inundations of this warm, shallow sea laid down thick sediments that would eventually become vast layers of dolomite, limestone, sandstone, chert, shale and clay mineral deposits.
While clay has served mankind well in many ways, including the manufacture of pottery, stoneware, porcelain, bricks, cooking vessels, primitive ammunition, smoking pipes, and building material, it does not serve well as a medium for growing plants. When dry, clay is very hard and prevents plant roots from growing deeply. It also tends to crusts over and crack, which not only strangles new seedlings, but actually repels water.
On the other hand, once clay has absorbed water (and it can absorb a lot of water!) it holds on to it for a very long time. While this property can be helpful during periods of heat and drought, it does nothing for plants during prolonged winter rains and snow. Because clay drains very slowly, plants are often suffocated and drowned or heaved from the ground during freeze-thaw cycles.
There is one good thing about clay that most people don’t consider when gardening – clay is very nutrient-rich, having high levels of magnesium, calcium and potassium. The challenge is forcing the negatively charged clay particles to release the positively charged nutrients so that plants can utilize them. In normal situations, this is easily accomplished through the application of lime and by the incorporation of organic material into the soil. Unfortunately, on an erosion-prone slope like ours, digging of any kind could trigger another round of erosion or even a small landslide. So what does one do, short of building massive retaining walls and filling them with topsoil, to vegetate a hillside?
In permaculture design, the goal is to take advantage of a negative by finding and utilizing the positive. From the very beginning, Dean and I made note of the weeds growing in small patches along the terraces, which can be seen in this picture. During the first phase, we purposely tried to avoid killing or removing them when at all possible. After weeks of searching for information on plants that would grow in heavy clay and finding nothing worth pursuing, we finally decided that our approach would be five-fold:
First: Anything that grows on the terrace – be it “weeds” or brambles or whatever – were to be allowed to grow unchecked. Better to have something sink it’s roots into the clay and hold on to it, than nothing.
Second: Every seed, plant, shrub, tree or bulb that we can get our hands on will be planted in whichever place looks the most promising.
Third: Every clump of grass or weeds dug out of the front yard or other areas(where we were preparing our veggie and herb gardens) was to be hauled to the flat upper decks of the terraces and to the rocky hillside above and “replanted” there.
Fourth: Every shred of organic material that might cling to the terrace slopes, such as grass, leaves, stems, twigs, et al, would be spread over the bare patches as decomposing, moisture-retaining “mulch”.
Fifth: Don’t give up.
As the summer progressed, we scattered pounds of clover, “replanted” wheelbarrows full of grass clumps and mulched, mulched, mulched. By winter of the first year, the situation was looking bleak. The lack of rain and intense heat thwarted all of our planting efforts. The good news was that the terraces were still holding and redirecting runoff.
By the time the following spring arrived, things began to grow and despite another summer of unprecedented heat and drought, all of the volunteer natives flourished. Some of the plants that volunteered on the terrace included yellow wood sorrel, pinks, curly grass, cinquefoil, pokeweed, cream indigo, rue anemone, frost grape, broom sedge, native sedge, evening primrose, blackberry, ragweed, small white aster and even a few passion fruit vines that produced a nice crop of fruit.
In addition to the native volunteers and some that were seeded by hand, we also planted bearded irises, grape hyacinths, naked ladies, daffodils, sedum, thyme, variegated vinca, mint, redbuds, curled tansy, peony and just about any other plant that we were able to divide or that were given to us by friends. Some did well and others didn’t and some we won’t know about until next spring.
One Year Later…
This spring, I plan on recycling mineral lick buckets into raised-bed planters. These planters will be positioned on the level platform at the top of the first terrace. The buckets will be filled with native earth and good soil and be sown with heat-loving and vining crops like melons and squash. The idea is to have the vines crawl all over the face of the terraces, shading and protecting the young perennials below and breaking the impact of heavy rain on the hillside. Not only will the terraces be secure and look gorgeous, but they will help accomplish one of our gardening goals, which is to have our “yard” produce food.
Until then, I’m happy just to be able to look out of my window at the terraces and not feel fear or trepidation at the first sign of rain. What I feel now when I look at them is a deep respect for nature’s ability to heal and a hopeful outlook for the future.
And while the terraces aren’t yet the show-stopper that I dream of, right now they are beautiful in a wild and natural way. And more importantly, they are no longer raw red sores bleeding across the landscape: they are stable, almost entirely covered with vegetation and no longer depositing silt into an already stressed watershed.
Stop back in the spring and see how our plans for the terraces are shaping up.
Until then, happy gardening!
Did you miss The Terrace Project: Year One (Part I)? Read it here!
© 2012 Jill Henderson
Jill Henderson is an artist, author and the editor of Show Me Oz
Jill’s work appears in several publications, including The Permaculture Activist, The Essential Herbal, Acres USA and Llewellyn’s Herbal Almanac. Her books on gardening, herbs and nature can be found in the Show Me Oz Bookstore.