Companion Planting: Myth or Reality?

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Companion planting doesn’t always live up to its promises.

I no longer believe in companion planting as such. From the mid-1970s through to nearly the end of the 1980s, I tried practicing the precepts of this technique only to get very mixed results.

Companion planting as we know it today is based on two books by Louise Riotte, Carrots Love Tomatoes: Secrets of Companion Planting and Roses Love Garlic. Ms. Rioux, who died in 1998 at the age of 89, was a charming woman I spoke to several times over the phone. She was a wealth of horticulture information, but even back then, I didn’t agree with everything she wrote. Especially when the subject was gardening according to the phases of the moon… but that’s another subject entirely. Let’s get back to companion planting.

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Companion planting chart: often more confusing than helpful.

I’m not saying companion planting is total rubbish. It includes many good and useful ideas… but they are buried among baseless beliefs, half-truths and misconceptions. And I certainly no longer make any effort whatsoever to follow those complex companion planting charts, created, theoretically, to help you choose which plants to grow next to which others. Talk about complicated! Oh, they are fine if you want to pick two vegetables to grow together, but once you try planting a garden with a variety of different plants, it all becomes so confusing you almost feel like abandoning vegetable gardening altogether!

Things that Don’t Work

Here are three examples of companion planting techniques that didn’t work for me.

Bunches of carrots for sale at the Farmer's Market

The book’s title lies: carrots actually hate tomatoes.

Carrots love tomatoes, the first book’s cover says. Well, good luck with that! Tomatoes seem totally fine with carrots growing near them: after all, they’re big, dominant plants that grab all the sun. Plus they’re a bit allopathic (see below). Why should they care about an insignificant little root vegetable growing at their base? Besides, I really pump up the organic matter when I plant tomatoes, adding lots of compost (they love rich soil), but carrots prefer leaner soil. But whatever the reason, the poor carrots suffer in the company of tomatoes, giving stunted roots. When the title of a book vehicles a false idea, what can you expect from the rest?

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In my gardens, nasturtiums don’t repel aphids, they attract them.

I was told to plant nasturtiums (Tropaeolum majus) in the vegetable bed to ward off harmful insects, especially aphids. But to my disappointment, my nasturtiums were frequented attacked by the very insects they were supposed to repel, then, if I did nothing, the pests would spread to nearby vegetables. I now use nasturtiums as trap plants: when aphids show up on them, I yank them out of the garden, nipping the upcoming infestation in the bud. That part of the equation never seems to appear in companion planting manuals.

 

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Marigolds are supposed to repel root nematodes… but what root nematodes?

Another example? French marigolds (Tagetes patula) are supposed to repel harmful root nematodes if you interplant them with vegetables, especially tomatoes. But this is one case that has been thoroughly studied by the scientific community. Marigolds have no effect whatsoever on root nematodes when used as companion plants, but will control them if the infested area is planted in marigolds alone. (Read Marigolds versus Nematodes for further information.) So interplanting with marigolds, although it may have other benefits (their flowers will attract pollinators, for example) will do nothing to repel nematodes.

I religiously planted marigolds among my tomatoes for years and never saw any sign of nematode damage. I was therefore convinced the tip worked… until I realized that none of the other gardeners in my community garden had problems with nematodes even though they weren’t growing marigolds. I did some research on the subject and it turns out that root nematodes are almost never a problem in home vegetable gardens, at least not in colder climates. So why put efforts into preventing a problem you’ll likely never have? I haven’t planted marigolds near my tomatoes in over 20 years and have still never had a problem with nematodes.

Common Sense Planting

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Common sense planting: mix up your veggies and give each the conditions they prefer.

Today I rather instead apply what I can “common sense planting”. For example, tall vegetables easily shade out their neighbors. So I plant them at the back of the garden, to the north or northeast. Lettuce, though, prefers a bit of protection from summer heat, so when I do a second or third sowing, I do it under taller plants. And I automatically add flowers to any vegetable garden in order to attract pollinators, but almost any flower will do, not just those specifically recommended in companion planting books.

Also, many plants attract beneficial insects. Not just pollinators, but insects that prey on the enemies of our vegetables, like ladybugs and lacewings. Plants with scented foliage, especially, seem especially good at this and what has more powerfully scented foliage than herbs? So mixing herbs known for their ability to attract beneficial insects, plants like tansy, dill, and fennel, into your vegetable garden is also “common sense planting”.

And I’m a big believer in the advantages of interplanting, the idea of mixing plants together rather than planting monocultures (homogeneous groups). I learned this from Ms. Rioux and will be eternally grateful to her for teaching me about it. Interplanting is a common sense way to garden because monocultures tend to concentrate the smell of a given plant, attracting its enemies. Interplanting, on the other hand, dilutes plant odors and can thus help confuse predators. For example, back when I used to grow my potatoes in rows, I had major problems with potato beetles, but now that I mix them in with other vegetables, potato beetles are no longer a problem.

Some plants give off toxic products that inhibit the growth of their neighbors. They’re said to be allelopathic. The sunflower (Helianthus annuus) is one: so I don’t plant sunflowers in the vegetable bed. Nor would I ever consider planting vegetables under a walnut tree (Juglans spp.), another allelopathic plant. Again, this is common sense planting.

Conclusion

I know that many readers may be surprised or upset by this “rant” against companion planting, but the technique, at least as advocated by Ms. Riotte, gave such mixed results when I tried to practice it that, basically, I was just wasting my time. I learned a lot from her, but little of the “effective stuff” (her books are full of all sorts of tips) had anything to do with companion planting.

And I’m not the only one who is less than enthusiastic about companion planting. Many organic gardening books remain strangely silent on the subject: some skip through the concept quickly, others don’t mention it at all. I get the feeling some authors are simply too embarrassed to bring up the subject!

And the former Editor-in-chief of the prestigious and much regretted magazine Organic Gardening, Mike McGrath, a man for whom I have a lot of esteem, once wrote the following: “’Companion planting’; a topic laced with more folklore, hopefulness, bad information and just plain hype than just about any other in the gardening world.” (Just so you won’t accuse me of taking a statement out of context, you can read more about what he said here: The Truth About ‘Companion Planting’.

His point of view exactly reflects mine: there are as many misconceptions as good gardening practices in companion planting, if not more. So, yes, I do practice a common sense form of companion planting, but am no longer blindly following Ms. Rioux’s suggestions.

Not everyone will agree with me about this and if you want to say so, go right ahead. Your opinions are always welcome.

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