What is a companion plant?

Companion plants help other plants grow.

Companion plants may enrich the soil by providing nutrients or organic matter.

They may provide shade or mulch for shorter plants or bare soil.

They may prevent pest problems by repelling unwanted bugs or by attracting beneficial insects.

Companion plantings combine more than one crop in a given area, so garden space is used efficiently.

What kind of plants make good companions?

Many herbs and flowers make good companions for vegetable crops. The best companion gardens are a diverse mixture of vegetables, herbs and flowers.

Some companions may actually add nutrients to the soil. This reduces the need to apply additional fertilizer.

What are some examples?

Plants with cup-shaped or open flowers are great for attracting beneficial insects. Borage is a great choice for attracting these garden friends.

Dahlias and marigolds will repel nematodes in the soil and nasturtiums will deter pests that attack the curcurbit (cucumber) family.

Beans will actually “fix” nitrogen from the air into the soil. Often strongly-scented plants will confuse insect pests as they are looking for vegetables.

What are some good garden companions?

One of the original companion gardens is the Three Sisters Garden, which has been used by Native Americans for generations. They plant corn with pole beans and then under plant with pumpkins or squash.

The corn provides a structure for the beans to grow. The beans add nitrogen for heavy-feeding corn. The squash leaves act as mulch by shading plant roots, reducing water evaporation and preventing weed growth.

Other examples include:

Sweet alyssum plants under broccoli or among potatoes will attract beneficial insects and prevent weeds from growing.

Potatoes and beans make a great combination. They tend to confuse each other’s insect pests.

Tall flowers provide needed shade to lettuce as the weather gets hot.

Heavily scented plants such as marigolds, basil and artemisia can be used to confuse pests.

Plant crops to trap unwanted insects. Potato beetles love eggplant and flea beetles love radishes. You can use these plants to monitor insect levels and, as plants become infested, they can be simply destroyed, bug and all.

Yarrow has insect-repelling abilities, too. Plus, its leaves make a great addition to compost.

Many herbs will attract the beneficial insects you want in the garden. Use flowers from the aster family like sunflowers, coneflowers, black-eyed Susans and daisies to attract these good guys. Plants from the parsley family (parsley, coriander, and dill) are also good attractors.

Experiment and see what works for you. Don’t forget to keep a record. You’ll want to duplicate your successes next year.

The key to a good companion garden is diversity.

This is only the basics of companion planting, but as you can see, it is a great way to reduce or even eliminate the use of pesticides in your yard and garden.

It is a proven, no cost method, of vegetable production. Organic gardeners have been using these practices for years.

“Growing Green” is contributed by Diane Dorn, Lehigh County Extension Office Staff, and Master Gardeners. Information: Lehigh County Extension Office, 610-391-9840; Northampton County Extension Office, 610-813-6613.