POOR AS IT IS, MY SOIL SITUATION IS COMMON. People who follow all the popular lawn-care recommendations are a lot more rare than lawn-care advertising might lead you to think--the homeowner whose idea of lawn care is to mow every week or so is blessedly commonplace. I say blessedly because, on the whole, less lawn care is far better for the environment. So I'm always happy to say hello to a neglected lawn.
But soil suffers when you run a mower back and forth over it year after year. If you rake up the cut grass and remove it, you also deprive the soil of nutrients. The result can be what I found when I moved into this house: compacted, nutrient-poor soil in which the healthiest plants are the weeds, especially the dandelions. Because of their long, strong taproots, dandelions can break up compacted soil and fetch nutrients to the surface from well below ground. Homeowners are supposed to regard dandelions as an enemy. Yet ironically, many lawns remain healthy largely because they do contain so many dandelions.
What to do if, like me, you want to replace that lawn with native plantings? Some people recommend an approach in which you till the soil, add amendments if you consider them necessary, water well to encourage weed seeds to sprout, then till again. This process must be repeated until all weed seeds have been brought to the surface, have sprouted, and have been tilled back into the soil. Only then can the soil be planted.
There are a lot of disadvantages to the till/water/till again approach: Tilling around trees can injure the roots, killing the trees. Tilling destroys any soil structure you already have. With this approach, you usually have to hold off planting for at least a year, as it takes at least that long to bring all the weed seeds to the surface and force them to sprout. Tilling requires extensive use of an internal combustion engine, which burns fossil fuels and is polluting. And finally, this approach is a lot of work!
Here's my much simpler, easier approach:
- Collect a lot of cardboard. Big pieces are better. Heavy cardboard is best. The cartons that refrigerators and other big appliances come in are ideal. Appliance stores will often give them to you for free.
- Order a big load of topsoil or compost. I usually order about 14 yards at a time, which makes a mound the size of a small car. That seems to be the outside limit of how much dirt I can move around in one season.
- Put the cardboard down on the ground. Be sure to overlap the edges so that every bit of ground is covered.
- Cover the cardboard with the dirt. Don't put down less than an inch or more than 4 inches; anything more than 4 inches can suffocate the roots of trees, which will kill them. (A few species of trees, such as Deodar Cedar, seem to be sensitive to even that much disturbance around the root zone. If you have a tree you're especially concerned about, consult an arborist.) However, try to spread the compost as deeply as you can up to that 4-inch limit.
- Plant the compost densely with a variety of inexpensive, low-growing native plants. I'll talk more about this the next time I post an entry in this series. Meanwhile, please note that, with this method, you can--and in fact should--begin planting right away.
- Water well. The cardboard under the compost will start to soften and disintegrate as soon as it's soaked. You can then put a spade through it and immediately plant any trees or shrubs you have planned for the space.
- Keep watering as necessary for the first few years. Once established, native plants don't usually need to be watered, but you do have to water them until they have established their roots.
- Weed occasionally. The cardboard and compost will smother most weeds. Because this approach buries weed seeds, you do not add to your weed problem by bringing weed seeds to the surface as tilling does. But some weeds always manage to punch through even the heaviest cardboard and thickest layer of mulch. Others blow in as seed, taking root in the compost. So occasional weeding will be necessary. I'll talk more about that in a later post.
- Relax and let nature do the rest of the work for you. That top layer of rich earth will soon attract earthworms; they'll eat their way up, feed, breed, and eat their way back down again. This eventually mixes the compost into the rest of your soil just as thoroughly, and far more gently, than tilling would have. Also, the more earthworms you have, the more earthworm castings you get--and earthworm castings, as everyone knows, are great for your soil.
Although this approach is, sadly, not work-free, it is far easier than any other method I'm familiar with for improving compacted, nutrient-poor soil.