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When a vegetable garden doesn’t look like a vegetable garden, what is it? A polyculture, where gardeners strive to address this simple truth: The most effective way to grow healthy plants is to create gardens that replicate nature. After all, nature is your silent partner that makes your garden work. In our newest book, “What’s Wrong With My Vegetable Garden?”, we frequently recommend polyculture as a sound organic gardening practice for managing pests and disease.
In a polyculture garden unrelated plants grow next to each other. Think of it as the opposite of a field of corn, the most classic example of monocultures. Like an English cottage garden, the mixed vegetable bed is aesthetically pleasing, and when you g
arden in concert with the natural world you garner many rewards. Pestiferous insects have more difficulty finding your vegetables. It becomes more difficult for diseases to jump from plant to plant. And, having a wide variety of plants attracts beneficial organisms from the wild.
Insect Pests and Polycultures
Insects home in on your vegetable plants from great distances by smell. Attracted by the scent, the critters fly directly to their hapless prey. If you have several tomato plants growing close to one another, the insects easily find them by their odor. However, as insects approach their target, they switch from olfactory to visual. If the target plants are hidden behind a wide variety of other kinds of plants, the insects get confused and have difficulty finding the tasty treats they’re after. Plant the same number of tomatoes, but scatter these around your yard. Surround them with other plants, including fruit trees and berry bushes, thus masking the tomato scent. Pests must work much harder to find and damage your produce.
Diseases and Polycultures
Diseases caused by fungus or bacteria easily hop from one plant to the next when they’re all planted close together in a row. Downy mildew decimates rows of beets in a conventional garden, whereas a polyculture approach avoids this tragedy by planting small patches of beets in different locations.
Diseases caused by bacteria and fungi leap from plant to plant in a variety of ways. Fungi spread by wind or water-splash from the ground. Bacteria are carried by insects, windborne rain, or on the gardener’s clothing (if the plants are wet). Viruses also attack when insects like aphids, leafhoppers, and thrips carry the disease from one plant to another. The closer together the plants of the same type are, the easier it is for disease to spread. It’s just like people on an airplane or in an elevator. When one person with a bad cold coughs the entire cabin of people is exposed to his germs.
Attracting beneficial organisms
Wild creatures that help you in the garden are everywhere. Birds, butterflies, bees, and hover flies all provide pollination services. Birds, wasps, beetles, and nematodes actually control harmful pests. Some birds, beetles, and nematodes can harm your plants, however, so strive to maintain a healthy balance in the garden. Everything you do to encourage your beneficial partners from the wild helps to create this balance. You can invite these helpers into your garden by growing those plants that attract them. These plants lure beneficials into your garden by providing food, nectar, and shelter.
A whole host of beneficial insects prey on the harmful insects that eat your garden. Most of us know lady beetles (aka lady bugs), and almost every gardener knows that lady beetle adults and their larvae eat aphids. But so do green lacewings, minute pirate bugs, hover fly larvae, and many more.
Many tiny wasp species lay their eggs inside caterpillars. When the eggs hatch, the baby wasps eat the caterpillar alive from the inside out. They burrow out of the caterpillar when mature and spin cocoons that hang on the caterpillar’s body like little cotton swabs. There are even tinier wasps that lay their eggs inside aphids! There are also mites that love to hunt down and eat all those spider mites on your roses.
Disguising themselves as bees to discourage predators, hover flies are actually quite harmless. The adults pollinate flowers and sip nectar. Their babies (maggots), however, kill and eat aphids. Check out our blog Beneficial Babies and click on the link to see a very short video of one of these predatory maggots exploring my rose bush.
Ladybird beetles (aka Lady Bugs) are some of our favorite and best-known beneficial insects. The adults and babies devour aphids and other small, soft-bodied pests. Fennel flowers are magnets that lure these small beetles into your garden.
Plants that attract a large number of beneficial insects are members of the carrot family (Apiaceae), the daisy family (Asteraceae), and the mint family (Lamiaceae).
The carrot family includes herbs such as dill, fennel, coriander (cilantro), parsley, and cumin, along with flowers like Queen Anne’s lace.
Daisy family plants to consider for your vegetable garden include herbs like tarragon and chamomile, and flowers like Cosmos, sunflowers, Gaillardia, Echinacea, bachelor’s button, and yarrow.
Mint family herbs include thyme, rosemary, lavender, catnip, horehound, and sage, and flowers include catmint, Agastache, and Pycnanthemum.
If you’ve been gardening for a while now, think about redesigning your approach to the garden to include polyculture ideas. If you’re planning your first vegetable garden definitely incorporate ideas from nature to make your garden work for you.
David Deardorff and Kathryn Wadsworth will present workshops at the Puyallup, Wash. 2012 MOTHER EARTH NEWS FAIR.
Please visit the FAIR website for more information about the Puyallup, Wash. FAIR June 2-3, and the Seven Springs, Pa., FAIR Sept. 24-25. Tickets are on sale now.
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