The Truth About Companion Planting In The Organic Garden
Does 'companion planting' really work to repel pests and grow more organic vegetables
, without chemicals? Is it one route to sustainability in the organic garden? Or is it a lunatic's nest of fable and anecdote? Answer: all these things! Many a gardener has overturned the myths of companion planting from personal observation.
I have successfully grown beans among onions, and fennel alongside tomatoes. I've personally twined runner beans up sunflowers with excellent results. Yet all these partners are said to hate each other, according to authoritative books on companion planting.
Conversely, some gardeners have also planted nettles beside carrots to attract beneficial insects, as some gurus advise, but have then seen the crop wiped out by carrot flies, sheltering in the nettles. Or they've reared pollen-rich flowers to attract beneficial insects to their vegetable blossoms, then been puzzled when the insects feast on the foxgloves - but disdain the runner beans. Or vice versa.
Does companion planting hinder or help?
Those very few scientific tests that have been done on companion planting, have raised serious questions. For example, setting aromatic plants among brassica, a popular recommendation, actually increased damage from caterpillars in some trials. It was found more effective simply to lay green plastic, even astroturf, beneath brussel sprouts, to make the plants invisible to the cabbage white butterfly.
Growing basil or nasturtiums with beans sometimes encouraged, rather than deterred, aphids. Potatoes grown with marigolds, horseradish, peas or garlic showed no benefit whatever and intercropping potatoes with broad beans - a legendary combination - often depressed the potato yield. In any case, horseradish is a risky companion for any vegetable plant. Future plots will never be free of it.
There was no measurable increase in yields, or drop in pest damage, observed when mixing cabbages and tomatoes, or runner beans and tomatoes, or radishes and cucumbers - all favoured companions.
Where companion plants did reduce pest damage, this was often offset by lower production. If tansy was grown thickly enough to reduce aphid attack on peppers and squash, or marigold was set among cabbages to deter flea beetle, the companions competed so vigorously they stunted the food plants. And so on.
Experts are poor companions
Gardening gurus also contradict each other. Bob Flowerdew's Organic Bible claims that brassica do well with tomatoes, yet Louise Riotte in Carrots Love Tomatoes says 'tomatoes and all brassica repel each other and should be kept apart'.
Robert Kourik in Designing and Maintaining Your Edible Landscape Naturally states 'sunflowers produce chemicals that act as growth inhibitors to a number of plants', and Bob Flowerdew counsels they should not be grown with runner beans. This will surprise those of us who gain bumper crops, by intercropping sunflowers with lettuce, indeterminate tomatoes, dwarf and climbing beans - including runners.
Mr Flowerdew is right to caution us but only because, in my experience, sunflowers massively dehydrate the surrounding soil, much as conifers do. But keep the area amply watered and theres usually no problem.
Indeed, shamefully little scientific research has been done in any area of companion planting. And so different are everyone's soil, micro-climate, pest and weed populations (and growing methods) that no single combination or prohibition, howsoever sensible it seems, will work as it should every time. If it does, distrust the evidence. Your crop may now be growing 'better' (or worse) because some quite different factor is at work!
Yet while any influence on pests, crop yields or weed control may be unpredictable or arguable, companion planting still merits study - if only because it makes the best pragmatic use of the soil.
Sensible companion planting
Companion planting can often work well, but for reasons that are not obvious. Simply, it makes the best available use of the soil and available light. Chinese cabbage and brussel sprouts, or roots and lettuces, or beetroot and kohlrabi are good companions because they like similar soil but draw nutrients from it at different depths. Dwarf beans and cucumbers, or leeks and celery, or runner beans and bush tomatoes all enjoy rich, moist soil but they take advantage of light at different levels.
Squash, courgettes and pumpkins provide moisture-retentive ground cover to sweet corn, while suppressing weeds. Lettuces draw lightly from the soil and grow well under runner bean trellises, even in moderate shade, so making productive use of an otherwise barren area. And so on.
Will companion planting work in your garden. Yes! But only if you replace superstition with common sense!
by: John Yeoman
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