Ask Linnea: Companion Planting

Q: What is companion planting?

A: Companion planting helps bring balance into your landscape. By using certain plants in your landscape or garden, you can attract beneficial insects and discourage harmful pests. It is key to organic gardening.

  • Alfalfa is a perennial with very long tap roots that are famous for breaking up clay soil. Alfalfa fixes the soil with nitrogen, and accumulates iron, magnesium, phosphorus and potassium. Alfalfa is pest-free, disease-free, and needs no extra water to survive.
  • Amaranth is a tropical annual that needs hot conditions to grow. Amaranth is a good plant for providing a home to predatory ground beetles.
  • Anise is an herb with a licorice flavor. Anise is host for predatory wasps that feed upon aphids.
  • Basil is said to improve the flavor of tomatoes, so plant these two together. Basil repels thrip, flies, and mosquitoes. Do not plant near rue.
  • Beans enrich the soil with nitrogen. Beans are good company for carrots, broccoli, beets, and cucumbers. Keep beans away from alliums (the onion family).
  • Bee Balm or Monarda can be planted with tomatoes to improve growth and flavor. Bee balm attracts beneficial bees.
  • Beets are great for adding minerals to the soil. Plant these companions with the beets: lettuce, kohlrabi, onions, and broccoli.
  • Catnip deters flea beetles, aphids, Japanese beetles, squash bugs, ants, and weevils. A safe way to repel mice is to put a sprinkling of catnip wherever you find evidence of them. And of course cats love catnip!
  • Chervil is a great companion to radishes, improving their flavor and growth. Chervil keeps aphids off lettuce and deters slugs.
  • Chives improve the growth and flavor of carrots and tomatoes. Chives keep aphids away from tomatoes, mums, and sunflowers. They drive away Japanese beetles and carrot rust fly. And they taste great in salads!
  • Coriander repels aphids, spider mites and potato beetles.
  • Dill improves the growth of cabbage. Do not plant near carrots or caraway. Dill is a great companion for lettuce. Dill attracts hoverflies and predatory wasps, and it repels aphids and spider mites. Dill seed can be sprinkled around squash to deter squash beetles.
  • Elderberry branches and leaves can be put into mole runs to banish them.
  • Flax can be planted with carrots, and potatoes. Flax can offend the Colorado potato bug.
  • Four-O'Clocks draw Japanese beetles like a magnet. Four-O'Clocks happen to be poisonous to the Japanese beetles. But be warned they are also poisonous to humans – so plant them away from children.
  • Garlic repels aphids and sometimes deer.
  • Geraniums repel cabbage worms and Japanese beetles.
  • Larkspur is a great one for attracting Japanese beetles and watching them die. But hear the warning; it is also poisonous to humans.
  • Lavender repels fleas and moths.
  • Leeks need to be grown near carrots, celery and onions. Leeks repel carrot flies.
  • Lemon balm can be used to deter squash bugs.
  • Marigolds attract aphids and slugs. Their roots keep the soil free of bad nematodes. French marigolds deter white flies. Mexican marigold has a very strong insecticidal repelling effect. It is said to keep bind weed from growing near it, and it may also keep beans and cabbage from growing properly. Mexican marigold repels Mexican bean beetles and wild bunnies.
  • Mint deters white cabbage moths, ants, rodents, flea beetles, aphids and improves the health of cabbage and tomatoes. As with catnip, mint also deters mice. Mint attracts hoverflies and predatory wasps.
  • Morning glories attract hoverflies and are an instant cover for your trellises.
  • Nasturtiums are used to deter whiteflies, squash bugs, and cucumber beetles. Nasturtiums do attract aphids, so plant them to trap these pests.
  • Onions can be planted with carrots, leeks, beets, kohlrabi, strawberries, broccoli, dill, lettuce and tomatoes. Keep onions away from summer savory and peas.
  • Opal basil is said to repel hornworms.
  • Oregano is a good companion for cabbage, broccoli, and cauliflower. It repels cabbage butterfly and cucumber beetles.
  • Parsley attracts hoverflies and parasitic wasps.
  • Peas fix nitrogen in the soil, so plant them with corn to provide extra nitrogen. Do not plant peas with onions.
  • Pennyroyal repels fleas and can be used to repel chiggers, flies, gnats, mosquitoes, and ticks when crushed and rubbed on your skin. Makes a great lawn alternative – there’s nothing like having a scented lawn.
  • Petunias repel asparagus beetle, leafhoppers, tomato worm, and Mexican bean beetle.
  • Rosemary repels cabbage moth, bean beetles, and carrot flies.
  • Sage deters cabbage moth, beetles, black flea beetles, and carrot flies. Do not plant near cucumbers, onions, or rue.
  • Summer savory discourages cabbage moths, Mexican bean beetles and black aphids.
  • Thyme deters cabbage worms.
  • Yarrow attracts predatory wasps and ladybugs.

This is just the beginning to many new companions in your garden. Find which ones work for you and discover your own companions.