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Companion Plants

© Kathy Reiffenstein

When planning a garden, the normal approach is to choose plants for their color, size, shape or scent. But consider this: choose plants that will help each other grow and you will create a healthier, more abundant garden. The theory is that certain plants can benefit others when planted in close proximity. Plants offering some mutual benefit are called companion plants and their interactions contribute to the creation of a balanced eco-system in your garden.

Companion planting has evolved from historical observation, horticultural science and gardeners’ ingenuity coupled with trial and error experimentation. Early settlers were taught by Native American gardeners to plant the “Three Sisters” – corn, beans and squash – because of their symbiotic relationship. Corn provided the structure for the beans to climb; the beans replenished the soil with nutrients; the squash leaves conserved water and controlled weeds. In our modern vegetable and flower gardens, there are many benefits to be derived from the symbiotic relationship of companion plants:

• Plants with strong odors attract, deter and even confuse certain insect pests. Planting something that is particularly attractive to damaging pests distracts these pests from the main crop.
• Certain plants, especially herbs, provide shelter, nectar and pollen for beneficial insects. The beneficial insects, such as ladybird beetles, lacewings, hover flies, mantids and various parasitic wasps, in turn prey on the insect pests, keeping them in check.
• Some plants give off nutrients needed by other plants.
• Certain plants improve the flavor or growth rate of other plants.

Must-haves in your garden are plants whose odors discourage unwanted insects from feasting on the succulent leaves and shoots of your favorite blooms. French marigolds (Tagetes patula), with strong odor in their leaves and flowers, confuse pests looking for their favorite plants. Marigolds also attract hoverflies which prey on aphids. The African species (T. erecta) releases a substance from its roots called thiopene which repels bad nematodes. The more of these attractive workhorses you can plant, the better.

Some of the most effective repellant plants are garlic and chives. Aphids and beetles are particularly deterred because of the strong scent. Underplanting your container roses with garlic is a good way to keep the armies of aphids in check. Nasturtiums (Tropaeolum majus) also deter aphids (especially black aphids), as well as cabbage worms, squash bugs and whiteflies. The yellow-flowering nasturtiums seem to be most effective. Sunflowers (Helianthus spp.) have long been used by gardeners and farmers to protect their plants. Ants will herd aphids onto the sunflowers and away from your more vulnerable plants. Sunflowers also produce plentiful seedheads, perfect for the birds.

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