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Napa County Master Gardeners: Build your soil for healthy plants
Master Gardeners

Napa County Master Gardeners: Build your soil for healthy plants

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Growing some of your own vegetables is one way to contribute to a more sustainable world. Locally grown food, if grown correctly, has a much smaller environmental footprint than food imported from elsewhere. The good news is that you can make your vegetable garden even more sustainable by a few simple practices: reducing the inputs, minimizing waste and building your soil.

Building your soil is the best thing you can do for healthy plants. It helps sequester (store) carbon, and it provides an opportunity to reuse garden waste on your property. I hope you compost your fruit and vegetable scraps (nothing diseased, though) and other garden waste.

Compost is a wonderful soil amendment and mulch. Natural biological processes will help break down those materials that need to break down, and earthworms and other soil critters will mix the amendments into the soil without your having to lift a finger.

Other things you can add to the soil include shredded newspaper (if your newspaper uses soy-based inks) and cardboard. You can use overlapping layers of cardboard covered with a layer of mulch to help control weeds. In those parts of your garden that stay moist, the cardboard will break down completely in three to four months.

It’s also a good idea to avoid tilling or turning your soil. Tilling or turning your soil reduces the organic matter in your soil. Most plants, once you’re done harvesting, can simply be cut down. Leave the root mass in the soil to add organic matter.

You can further improve your soil and store more carbon by growing cover crops. Don’t turn the cover crops into the soil; just cut them down, chop them up and leave them in place as mulch.

Reducing inputs simply means buying less stuff to support your garden and using less water. By now, we know how to reduce our water use: use drip irrigation, mulch and monitor your plants to make sure that you don’t over- or under-water them.

So how can you buy less “stuff” such as plants and seeds, fertilizer and weed- or pest-control products? To reduce your need for fertilizers, you can plant cover crops in the winter, especially legumes such as fava beans to fix nitrogen in the soil. In healthy soil, nutrients already in the soil are more available to your plants.

If your soil does need more nutrients, try to find local sources of manure. (Manure should be composted before it is applied to your garden.) If you buy fertilizer, apply the same principles that you do for your other purchases: figure out where the ingredients come from, and buy as local and sustainable as possible.

To reduce your purchases of plants and seeds, grown your own plants from seed, share your seeds with other gardeners, and save seeds from open-pollinated varieties. It makes sense to share your seeds because fresh seeds (no more than two years old) produce the best plants.

Growing your own plants from seeds is fun. It allows you to grow more varieties than you can purchase and to have plants when the nurseries may not carry them. For example, the ideal time to set out broccoli and cauliflower seedlings for fall harvest is in mid-August, but just try finding seedlings for these crops in nurseries in August.

Some of the best ways to control weeds are to control where you water using drip irrigation. Mulching also helps minimize weed germination, or you can hand-pull or hoe weeds, of course. As long as a weed has not set seed, add it to your compost. It’s just more organic matter. Bindweed (field morning glory), blackberries and Bermuda grass can sprout from bits of stems and roots, so allow them to dry out completely before adding them to compost or using as mulch.

Healthy plants, properly tended, will be most resistant to pests and diseases. For insect pests, you can hand-pick the critters. (I sometimes shake plants over a bowl if a plant has been invaded.) Or you can wait for natural predators to arrive and take care of them for you. Look first to non-toxic methods, such as spraying aphids off with a garden hose

If you hand-pick critters, cool mornings or evenings are best because insects will be much slower when it’s cold. Plants also have their own forms of defense. They produce compounds in their tissues to help deter predators. Consider ignoring some damage. Plants communicate with each other through hormonal signals from their roots, and the plants near the one that is being attacked will also produce defensive compounds.

There are many ways to make your vegetable gardening more sustainable. The important thing is to keep improving.

Master Gardener Workshop: “Growing Tomatoes in the Home Garden” on Saturday, April 4, from 9:30 to 11:30 a.m., at the UC Cooperative Extension, 1710 Soscol Ave., Napa. Learn tips and tricks for cultivating great tomatoes including the latest research on care. Online registration (credit card only) or mail-in/walk-in registration (cash or check only) or call 707-253-4221.

The UC Master Gardeners of Napa County are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website ( or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.

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