Modern gardeners are rediscovering the art of companion planting
– an old-fashioned method of combining species that work together to help each
other thrive.
My childhood friend’s grandmother had what some thought was a
messy garden. Rather than planting rows and rows devoted to tomatoes, then more
rows of carrots, she intermingled various species. She also tucked small plants
here and there at the feet of taller ones. And – to the particular disdain of my
mother – mixed vegetables and flowers in the same garden.
At the time, I thought her garden was beautiful, with all the
mixed textures, colors and sizes of plants. And I now realize that it also must
have been highly productive, despite her refusal to use chemicals in her organic
garden. The method behind her intermingling madness is called “companion
planting.” And that simply means organizing the garden so that plants that
benefit each other’s growth are placed in close proximity to each other.
The first benefit is more to the gardener than the plants, and
that is optimal use of space. My friend’s grandmother must have had a small
garden, given the small size of inner city lots. But companion planting allowed
her to make good use of all the available room, using the space in the shade of
corn plants to grow lettuce, for instance.
The focus of companion planting is that many plants have
beneficial properties that can help other plants. By creating a balanced
ecological system in your garden, you work with Nature to ensure that all
the plants thrive, not competing for light or nutrients, and fending off
pests and diseases.
This happens in a variety of ways. Sometimes, a plant is
attractive to insects and, when planted beside the main crop, will protect
it by luring the insects away. This is called “trap cropping.” A good
example of this is when collards are planted to protect cabbages from moths.
Likewise, nasturtiums are useful as a vegetable garden trap plant for
aphids.
Other companion plants assist by attracting beneficial
insects, including pollinators, to the food crops. And others, like many
herbs, are useful in repelling insect pests. And therein lies the reason why
my friend’s grandmother grew garlic among her rosebushes and raspberries.
Garlic repels aphids, spider mites, fruit tree borers and even Japanese
beetles. Mint is useful against ants and white cabbage moth, rosemary deters
carrot flies and bean beetles, and horseradish helps against potato bugs.
Insects attracted by certain plants can also be beneficial
to both them and their companion plants. As well as fending off harsh
environments, diseases and pests, plants need to be pollinated to ensure
their survival. Visiting insects do just that.
Some plants exude chemicals that suppress or repel pests and
protect neighboring plants. The African marigold, for example, releases
thiopene – a nematode repellent – making it a good companion for a number of
garden crops. Rye can be used as a mulch around tomatoes and broccoli
because it leaches a chemical that prevents weed germination.
Legumes like peas, beans and cloves have the ability to fix
atmospheric nitrogen for their own use and for the benefit of neighboring
plants via the Rhizobium bacteria. Hence, the indigenous practice of
interplanting beans with corn.
Plants can create beneficial habitats for each other. For
example, tall-growing, sun-loving plants can share space with lower-growing,
shade-tolerant species, resulting in higher yields. This style of planting
can have other benefits too. The canopy resulting when corn is
companion-planted with squash or pumpkins – another indigenous practice – is
believed to prevent damage by the adult squash vine borer. And the prickly
squash vines discourage raccoons from eating the corn.
When dense plants protect vulnerable species by shading or
by creating a windbreak, this is called “nurse cropping.” Nurse crops such
as oats have long been used to help establish alfalfa by smothering the more
competitive weeds.
Companion planting has been used throughout the centuries,
with some sources suggesting that it was the early Greeks and Romans who
first recognized that certain plants could encourage or inhibit the growth
of others. Gardening journals and word-of-mouth through generations of
farmers and gardeners kept the knowledge of companion planting alive.
Although my friend’s grandmother’s companion planting methods were probably
scoffed at more often than praised, scientists have more recently begun to
verify the folklore and further the understanding of why plants enjoy the
company of certain other species.
Wendy Priesnitz is
the Editor of Natural Life Magazine and a journalist with over 35 years of
experience. She
has
also authored nine
books.
Visit her
website.
