If you have ever tried to grow things in sticky slick angry orange Alabama red clay, I won’t need to explain to you why I’m interested in improving it. The before picture is a representative sample of what the soil on my property looks like, and what the garden started as– a thin layer of darker topsoil over a deep bed of orange clay with chunks of chalky or cherty rock. Plants will grow in it, but it’s not great. Water tends to pool on top when it’s wet, then it gets hard brick dry in the summer. The after picture is what my garden beds look like now– you can still see the orange clay about a shovel blade deep, but now it’s overlaid with six inches of black crumbly fertile top soil and decaying organic matter, rife with earthworms and healthy biota. It’s a loose sponge ready to store water, facilitate air movement, and feed happy roots. The good news is that I can tell you how to do this with your clay. The bad news is that it takes time and steady effort; these are the results I’m getting after six years of the improvements I’m going to suggest in this post.
The short answer to clay improvement is add organic matter. This works to improve the soil pretty much any way you want to do it, if you add enough material over a long enough time. But I am going to describe a system that I have arrived at by trial and error that does several other useful things as well– reduce or eliminate the need to weed, reduce the need to water, reduce my household waste production, and take advantage of free inputs while helping out local businesses.
Here’s what one of my beds looks like before I do anything to it in the spring. I pulled tomato cages and cut down basil here back in the fall, and since then I have done NOTHING. Note the general absence of major weeds. The weeds you see are mostly easy to kill spring stuff, henbit and whatnot. It’s not taken over with grass, and it’s not a forest like it would be if I had left open tilled ground to grow up.
The first step is to flatten any weeds and add fertilizer. In this case, I added a some compost. I just dump it on top of last year’s bed, no need to dig it in. I let the worms do that for me. Compost is a topic for another post, but for the moment it’s enough to say I compost almost every waste product I produce, and I always wish I had more compost. This might be a two inch layer, I would go four or six if I could. I also put in rotted wood chips from the walkways between the beds. When they get rich enough with worm castings that they start sprouting weed seeds, it’s time to scoop em into the beds and replace with fresh wood chips.
Next, I add a layer of cardboard as a weed barrier. I stockpile cardboard all year, and it’s really satisfying to do something about the overload of cardboard box waste that our online shopping economy produces. As the permaculture folks say, there are no waste products, just unrecognized inputs for other processes. I recycle all the boxes I end up with, and then go get more. Furniture store dumpsters are the best, I want big continuous sheets of cardboard if I can get it. It’s important to overlap pieces and cover any holes, otherwise weeds will find their way through. When I get ready to transplant my seedlings into the bed, I will have to cut holes in it and plant through them, but it’s worth the trouble to me. I’m just not much of a weeder, and a few months of relative weed freedom is worth anything to me. After that it will break down enough that weeds can push through it, but by then my summer veggies will be filled out enough to shade the ground and discourage most growth if I space them tight enough.
The final step is to cover the cardboard with mulch. I’m shooting for six inches deep or more, it will shring substantially as it settles and rots down. Whatever kind of mulch you can get for free in bulk will do. On occasion I have bought pine bark mulch by the scoop for this and it works fine, but I like free better if I can find it. The city used to vacuum up people’s leaf piles at the curb in the fall and deposit them in a giant heap behind the botanical gardens. That was great mulch, but they stopped doing it. Now I’m getting wood chips delivered for free by the truckload from https://getchipdrop.com/. ChipDrop is a great service that connects gardeners with tree service companies. Gardeners get free wood chips, and tree service folks get to save on dump costs. Everybody wins and less stuff goes in the landfill. It remains to be seen if adding large quantities of wood chips will absorb too much nitrogen, but I’m not worried about it. I can just add more nitrogen at the compost/fertilizer step via manure or blood meal if I start to see signs of nitrogen deficiency.
That’s the whole process, and this bed is ready to plant. I will expose the cardboard and cut a hole in it where I want to plant each seedling, and that’s all I have to do. Usually some weeds will come up at the edges and through the holes, but it’s minimal. This bed will sponge up water when it rains, and retain it for a surprisingly long time. I usually water newly transplanted seedlings until they get established, and then little or not at all after that. They just don’t need additional water unless there is a serious drought.
The only downside to this system is that it does not readily accommodate direct planting from seed in blocks. You can leave gaps in the cardboard to make rows for direct seeding; I often do this along the fence to grow vining crops like beans, cucumbers, and gourds. I have sometimes done the same thing to make rows for seeding spring and fall leaf crops like collards and kale. You can grow things like winter squash and melons by seeding into holes in the cardboard. But if you want to seed a larger block densely (for baby greens for example) you pretty much have to disturb the surface and forgo the cardboard and mulch. I keep half a bed prepared this way for greens, and I rotate the greens patch among the four beds from year to year so that every bed gets about the same amount of soil improvement.
So there you have it. Fix clay soil, grow happy plants, suppress weeds, save water effort and time, recycle waste products, help local businesses, and save the world!