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Published: Thursday, March 24, 2005, SEATTLE POST-INTELLIGENCER

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The well-made bed: Pile on the compost

By Ann Lovejoy
SPECIAL TO THE POST-INTELLIGENCER

In several recent articles, we looked at design and maintenance techniques that can help your garden become more resilient and less needy. Here in the maritime Northwest, our soils can be challenging. Whether you garden on hardpan, heavy clay or lean, sandy soil, it is important to create a positive soil profile when building your beds.

This means that the height of the soil in your beds will be greater than whatever surrounds them, whether paths, lawn or paving. This mounding may be slight -- a matter of a few inches -- or significant, with bed heights ranging from 12 to 18 inches above grade.

The point of this is twofold. First, mounded beds provide positive drainage, encouraging excess water to flow freely away from susceptible plant roots during the rainy season. Here in the Northwest, we lose far more plants to winter rots than to cold.

Secondly, mounded beds allow oxygen to reach plant roots, resulting in larger, stronger root systems. Husky, healthy root systems are the key to creating resilient gardens that thrive with what I call benign neglect. Well-rooted plants are better able to provide their own nutrients, including water, so they are less dependent on human aid.

Another key piece is the layering on of amendments such as compost and alfalfa meal, instead of tilling them. In recent years, soil scientists have learned that tilling destroys natural soil biotic communities, weakening the soil structure. In contrast, annual layering with compost and other nutritive amendments feeds the soil biota without structural damage.

This is good news, since layering is much easier than tilling. However, since compost is now recognized as a vital ingredient for healthy gardens, quality counts. Poor quality compost can be a real problem, damaging plants and soil alike.

Why? Immature compost is full of degraders, bacteria and other little critters that actively break down both plant roots and beneficial soil biota. Raw compost can be hot enough to burn lawns and plants alike, so you end up paying for something that harms the garden.

Since healthy, mature compost can heal the garden from the ground up, it's well worth seeking out a reliable source. Many readers have asked how to tell whether compost is ready to use and of good quality. To differentiate a good compost from a potentially harmful one, use your senses: look, smell and feel.

Begin by evaluating the smell. Mature compost should smell pleasant, like freshly turned earth. It should not stink so badly that you and the neighbors need to shut all your doors and windows for several days. It should not smell like rotting wood chips or fermented fir bark.

In your hand, compost should feel a bit looser in texture than good garden soil. Good compost will clump a little, but won't squeeze into hard balls as clay does or sift through your fingers like sand.

Mature compost is an earthy brown and should be of fairly even texture. Good compost won't turn your hand black when you handle it. Some of the worst compost I've seen leaves a residue like dye that stains clothing as well as skin.

Mature compost may well have some identifiable bits in it, from pine needles to egg shell scraps. However, these bits should be much smaller than a stump or a tractor seat (both of which have been delivered to my home in loads of "compost").

However, these simple tests can tell you only that the compost is mature and won't burn your plants. They won't tell you if it is old and less biotically active than is desirable. Old compost may be perfectly usable and will add desirable tilth to your soil. However, to be truly nutritive, compost needs to be biotically active and diverse.

The best way to tell whether compost is of high quality is to have a sample tested scientifically, something that every reputable compost producer does on a frequent basis. If your compost supplier doesn't have recent and comprehensive test results or can't explain them to you, find a new supplier. Stick with materials that are safe and tested.

Here in the Seattle area, we are fortunate to have a deservedly reputable supplier of good quality compost. Cedar Grove compost is tested for a wide range of pathogens and residual pesticides as well as for maturity. This local company has worked hard to develop a safe, healthy and consistent compost and has earned a reputation for standing behind its product.

When making or improving beds for edible plants, the quality of your topsoil is equally important. Nearly all topsoil is artificially made with a range of materials, again often of varying quality. For the past few years, the best I've seen has been Cedar Grove's vegetable garden soil mix, a blend that is also terrific for ornamentals.

To order or check on compost test status with Cedar Grove, call 877-764-5748.

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Ann Lovejoy can be reached via mail at: 8959 Battlepoint Drive N.E., Bainbridge Island, WA 98110. Her latest book is "Ann Lovejoy's New Fresh From the Garden Cookbook: Recipes Inspired by Kitchen Gardens" (Sasquatch, 208 pages, $22.95).

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