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Your garden may look like an oasis of tranquility, but it is a hotbed of activity. It is home to billions of soil organisms involved in a drama of life and death, creation and destruction. These life forms, and the underground world they help create, are the key to a healthy, productive garden.

We are all familiar with the earthworm, known for helping to decompose dead materials. As it undulates through the earth looking for food, it also lightly tills and aerates the soil. Soil bacteria, another important decomposer, break down dead plants and organisms into nutrient-rich humus.

Mycorrhizal fungus is present almost everywhere plant roots are, providing plants with hard-to-obtain nutrients in exchange for sugars the fungus can’t produce itself. Microfauna, minute creatures such as nematodes and mites, are also present in mind-boggling quantity and variety.

The activity of these organisms is an important factor in soil structure, helping determine how mineral particles clump. An ideal soil structure has regularly spaced pockets, or pores. These pores allow water and air to move through the soil and reach plant roots. For the mineral particles to clump in an ideal way, they need a fourth ingredient: organic matter. Organic matter, largely created by underground life, is the glue that binds soil.

Many people till their garden in spring, adding a fresh bag of soil from the store, followed by some fertilizer. I call this the “quick and dirty” method. But you can get the same (likely better) results with less time, money and effort.

As is true for many Napa Valley gardens, my soil at home was nearly impenetrable initially. That first spring, as my wife and I began planting, the air was filled with groans of pain and muttered profanities.

The following fall, I received some helpful advice: stop tilling. When soil is tilled, it becomes compacted and hard. All those wonderful pores disappear. Without space for air and water, the soil ecosystem cannot function well, and your garden will suffer.

Instead of tilling in new soil, try adding a layer of mulch. Generally speaking, mulch is anything that covers the surface of your garden. While that definition includes non-organic materials, I highly recommend using organic matter such as compost, bark, grass clippings or even shredded newspaper.

Any mulch will help retain soil moisture, but organic options also feed your soil ecosystem. As the organisms break down the mulch, they produce nutrient-rich humus that helps feed your plants. Humus and certain soil organisms bind the soil, creating space for air and water. These conditions encourage even more microfauna, plant roots and bacteria. Over time, your garden bed will become softer, more workable and a much more pleasant home for your plants.

In vegetable gardens, a cover crop can also improve the soil. Instead of leaving a bed empty, sow fava beans, clover, peas or mustard. These plants enrich the soil as they grow and can then be mixed into the soil as “green manure” when you are reading to plant again. You can simply mowing them or hand-pull them and leave them on the surface to decompose. Or you can till them into the soil gently, disturbing only the top inch or two of earth.

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I have seen firsthand the almost magical change that you can achieve through proper soil care. The dirt in our garden used to be pale, dense and lifeless. After just one year of mulching, we had true soil, full of color and life.

The key to this approach is patience. It takes time for the underground ecosystem to grow and change the soil. But the reward is worth the wait. Take comfort in knowing that billions of tiny organisms are doing much of your work for you. The result will be more time to enjoy the fruits (and vegetables) of your labor.

Garden Forum: Join the U. C. Master Gardeners of Napa County at a forum for home gardeners on Sunday, March 12, from 1 p.m. to 3 p.m., at Yountville Community Center, 6516 Washington St., Yountville. Bring your questions about anything in the home garden. Questions about fertilizing, watering, planting, plant care, diseases and pests, tools and tool care or nursery purchases are welcome. Register with Yountville Parks & Recreation or contact 707-944-8712.

Workshop: U.C. Master Gardeners of Napa County will conduct a workshop on “Growing Tomatoes” on Saturday, March 25, from 9-11 a.m., at Connolly Ranch Education Center, 3141 Browns Valley Road, Napa. Tomatoes aren’t fussy. They just like the right place to grow and the right amount of water and basic care. Learn about proper soil temperature at planting, tomato types, support systems and environmentally sound pest and disease control. Online registration (credit card only); Mail-in registration (check only or drop off cash payment).

UC Master Gardeners of Napa County ( answer gardening questions on Monday, Wednesday and Friday, 9 a.m. to noon, at the UC Cooperative Extension office, 1710 Soscol Ave., Suite 4, Napa, 707-253-4143.