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 presented 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.
You can also get FAIR updates on our Facebook and Twitter pages.
