If a plant is doing poorly, there's a good chance it has something to do with the soil. Maybe it's lacking nutrients (find out with a simple soil test). Or it could be compacted from being trampled by people, animals, or heavy equipment. Plants growing in compacted soil cannot develop good root systems (making them more susceptible to drought), so the soil needs to be loosened and aerated.
Quite often, bad soil health is a question of the soil's texture. Pick up a trowel's worth and put it in your hands. Does it feel gritty? Too much sand. Is it powdery? Too much silt. Is it harsh when dry and sticky when wet? Too much clay. A good organic garden soil is dark and crumbly and literally full of life. Fortunately, no matter what the texture, all soil can be improved over time by incorporating organic matter into it.
Take sandy soils, for instance. They're made up of relatively large soil particles, so water and nutrients run through those gaps relatively quickly. Adding organic matter helps sandy soils retain both moisture and nutrients for plants to use.
Clay soils are just the opposite. They contain very small, densely packed particles that hold moisture but don't allow much air space for plant roots. Compost helps separate those tiny clay particles so water can drain more freely and plant roots can get needed oxygen.
GOOD TO KNOW: Not all soil is created equal—even in the same yard—because of soil disturbances from construction and excavation. Often the topsoil is removed during construction, leaving inferior subsoil capped with a thin layer of topsoil. Stick a shovel in the ground and you will immediately see this barren subsoil (orange in well-drained sites, grayish in poorly drained sites), which is incapable of sustaining plants without frequent applications of fertilizer.
For quickest results when creating a good organic garden soil, add compost, or the decomposed remains of plant materials. Compost keeps soil from baking and cracking during drought and encourages water to penetrate the ground rather than run off. Compost also introduces beneficial microbes—bacteria and other microscopic life forms that make soil more productive. Simply spread 3-4 inches of compost on a bed, then use a shovel or tiller to incorporate the rich organic material into the soil. You can buy compost in convenient bags or in bulk by the truckload, or you can easily make it yourself.
You can add other forms of organic matter to the garden to feed earthworms, which in turn aerate and fertilize the soil. What sorts of things should you add? Coffee grounds, banana peels, eggshells, shredded leaves, grass clippings, wood ashes (in small amounts), and sawdust are some examples. You can also buy bagged soil amendments such as peat moss, composted cow manure, cotton seed hulls, and potting mix (it contains perlite, a lightweight potting additive that aids aeration and water retention).
If you have heavy clay soil, you may be tempted to add sand, thinking it will improve drainage. But the sand can actually bond with the clay to form a virtual concrete. It's better to use gypsum, which makes fine clay particles lump together into larger particles, creating air pockets that aid drainage and allow oxygen to reach plant roots.
GOOD TO KNOW: A soil profile shows how soil is layered. The thin top layer is dark brown to black and consists of decomposed and semidecomposed organic matter. Below that is the topsoil, which is typically deep brown in color and is the layer of soil richest in organic material. It can be practically nonexistent in some areas due to erosion, or several feet deep in the Corn Belt and Great Plains states. Below that is the subsoil, a claylike base with minerals but few nutrients.
If you're making wholesale changes to a large area, your best bet is to sow a cover crop. A cover crop is a quick-growing annual such as buckwheat, clover, rye, or barley that is turned over before it matures. It's also called green manure because plants are plowed back into the soil when they're still green and immature (that's when they're highest in nitrogen). Cover crops are useful for reclaiming very poor soils with very little organic matter.
Try this cover crop rotation: Sow a thick crop of buckwheat, turning it over when it reaches 8-10 inches in height. Wait two weeks and sow another crop of buckwheat, again plowing it under when it's 8-10 inches tall. Let the ground lay fallow until mid-fall, then finish with a heavy sowing of winter rye; plow that under in spring.
There is also an old practice called double-digging. It's labor-intensive, but it is the best remedy for poor soil that includes hardpan, a subsoil so compacted that it's nearly impenetratable by plant roots. Double-digging involves temporarily removing the topsoil so the hardpan beneath it can be loosened.
Start by excavating a row at the end of a garden bed. Dig about a foot deep, saving the soil on a tarp. Now loosen the hardpan by sticking a spading fork deeply into the hardpan and twisting it around. Don't turn the soil over. Add an inch of compost, then fill the trench with the soil you remove from the next row. Continue excavating row after row until you reach the end of the bed. Use the soil you placed on the tarp to fill the last trench. A good finishing step is to top the bed with a couple inches of compost.
Nature has improved its soil for eons by recycling organic matter. Unlike chemical fertilizers, it's an environmentally friendly, long-term solution to soil fertility and productivity.