Organic Pest Control Technique Number Two: Companion Planting

Companion planting involves planting different kinds of plants together so that at least one provides some benefit to the other – sometimes, they are mutually beneficial. These may be two kinds of vegetables, or a vegetable with an herb or with a particular flower.

It is an art more than a science. Some traditional gardeners don’t like how this method can give their garden a messy look. Also, the novice companion gardener can easily inadvertently plant things too close together. When I first delved into the world of companion planting, I planted a borage seedling next to a zucchini. I had no idea that borage spread so widely – and was so prickly! Another time I grew a couple of tarragon plants, thinking that they would be like oregano and spread slowly and lowly close to the ground.

Nope. After a couple months, I realized that if I didn’t start pruning them severely, they were going to take over not only the garden, but possibly the lawn as well. So, does companion planting really work? It depends – not so much on whether the method is based on old wives’ tales, but more likely on your particular growing conditions, such as soil type and climate. Whether a particular companion planting works may also vary depending on the variety of crops you select.

Some people swear by certain pairings, while others see no positive benefits to the same pairing. For example, radishes are supposed to repel the cucumber beetle. But the year I tried growing radishes next to the cucumber vine, they had beetles nonetheless.

Still, many companions do work, and mixing up plant varieties in a certain area is a lot more natural than growing one single crop for rows on end. This may be why, in nature, you don’t see a lot of pest infestations on a particular plant: it is able to hide itself among different plants, making it harder for pests to find. I once heard a homesteading podcaster mention that if you grow just a few stalks of corn, you probably will never see a cornworm, but if you are growing acres upon acres of corn, you are essentially ringing the dinner bell for the little pest.

Certain companions help each other (or one helps the other, as the case may be) to grow better. Even though we want to focus on preventing pest problems, I’ll include some of those pairings in the list that follows as well, because you may find it to be helpful information.

Here is a sampling of popular companion pairings:

• Marigolds with cabbages and potatoes to control nematodes; with tomatoes to help prevent verticillum wilt. They repel most pests and attract beneficial insects.
• Marjoram and tarragon anywhere and everywhere both to confuse pests and to improve flavor of other crops.
• Garlic helps beets to grow; also may repel root fly.
• Rosemary, dill, basil, thyme, borage and sage all help to repel the cabbage moth (which will attach any brassica – broccoli, cauliflower, kohlrabi, kale, brussel sprouts – not just cabbage).
• Chervil keeps aphids off of lettuce, deters slugs, improves the growth and flavor of radish, broccoli and lettuce.
• Chives keep aphids away – do not plant any member of the onion family with legumes.
• Leeks with carrots to repel the carrot fly.
• Asparagus with tomato, because the solanine in the tomato protects from the asparagus beetle.
• Nasturtiums with melons to keep the aphids away.
• Dill improves the flavor of the brassicas.
• Petunias reduce the appearance of squash bugs, potato beetles and bean beetles.
• Rosemary around the perimeter of the garden as a hedge repels pests in general, mosquitoes in particular.

If you decide to incorporate companion planting into your organic garden – as I urge you to – be sure to design your garden so you end up with plenty of extra space for herbs and flowers. Also be sure to look up the height and spreading distance of each plant, so you don’t end up with similar problems as I did with the borage and tarragon.