"Companion Planting" & Organic Gardening

Phyllis Heuerman
Frederick County Master Gardener Program

Companion planting can be described as growing two or more different kinds of plants close together so that some benefit is derived, like repelling pests, attracting beneficial insects, adding needed nutrients to the soil, or providing shelter.

Companion planting is not new. For centuries many Native American tribes throughout North America have cultivated corn, beans and squash together. The Iroquois called them the "Three Sisters." Although the tribes did not know the scientific basis for it, they knew these crops thrived together. Corn provides a structure for the beans to climb. The beans replenish the soil with usable nitrogen and other nutrients, and the large leaves of the squash provide a living mulch that help conserve water and provide weed control.

If you have seen vineyards in the western United States you will often see rose hedges along the vineyards. Although they are beautiful, they are not just for show. Roses are susceptible to many of the same diseases as grapes, but the show symptoms sooner. If the vintners see signs of disease on the roses, they can take action to treat the grapes before symptoms occur on them.

Another kind of companion planting is called trap cropping. As an example, cucumber beetles, which transmit bacterial wilt, prefer squash and pumpkin pants over cucumber and melons. If you want to protect the latter and are willing to sacrifice the former, plant them close by.

By using companion planting, many gardeners find that they can discourage harmful pests without losing the beneficial allies. It can combine beauty and purpose to create a beautiful garden. There are many varieties of herbs and flowers that can be uses for companion plants. Experiment and see what works for you.

Here are some examples of companion planting:

  • Four-O'Clocks draw Japanese beetles which then eat the foliage. The foliage is poisonous and kills them. Plant them in your yard, away from the roses to draw them. Be aware, though, that they are also poisonous to humans. Do not plant Four-O'Clocks if you have small children.
  • Garlic repels aphids and is good to plant among your roses. It also accumulates sulfur, a naturally occurring fungicide which helps in disease prevention. Garlic also repels Japanese beetles, root maggots, and carrot root fly.
  • Basil helps repel mosquitoes and flies. Plant it near your door or patio.
  • Beans like to be near celery and cucumbers but dislike onions and fennel.
  • Cucumbers like corn, peas, radishes, beans and sunflowers. They dislike aromatic herbs and potatoes.
  • Monarda, or bee balm, attracts beneficials, including bees. Plant near crops that require bees for pollination, but be aware that it is invasive and susceptible to powdery mildew. You can plant it in pots to control its spread.
  • Catnip deters flea beetles, Japanese beetles, squash bugs, ants, weevils and mice. Of course, it does attract cats!
  • Chives improve growth and flavor of carrots and tomatoes.
  • Dahlias repel nematodes.
  • Plant tomatoes with carrots, onions and parsley. But keep cabbage plants away from them.
  • Dill seems to improve the growth and health of cabbage and seems to repel aphids and spider mites to some degree. However, it does attract the tomato horn worm so keep it away from your tomato plants.
  • Lavender repels fleas and moths. Prolific flowering lavender nourishes many beneficial insects.
  • Marigolds seem to repel many harmful insects, although they do attract spider mites and slugs. They can help deter whiteflies when planted around tomatoes.
  • Nasturtiums deter wooly aphids, whiteflies, squash bug, cucumber beetles and other pests of the cucurbit. Plant them as a barrier around tomatoes, radishes, cabbage and cucumbers. As a bonus, the flowers, leaves and seeds of nasturtiums are all edible!
  • Petunias repel the asparagus beetle, leafhoppers, some aphids, tomato worms and general garden pests.
  • Planting sunflowers with corn is said to increase yield. They also will attract aphids away from other plants, while they are so tough that the aphids do not damage them.

These are just a few examples of plant companionships that seem to work. To learn more about this subject search "Companion Planting" on the internet, or there are many books available. I like Carrots Love Tomatoes: Secrets of Companion Planting for Successful Gardening, by Louise Riotte

Read other articles on ecological gardening & native plants

Read other articles by Phyllis Heuerman