The belief that plants have an effect on one another in the garden is an ancient, but altogether modern concept.
Like fashion, horticulture trends come and go, but gardeners continue to pass along the principles of companion planting, which basically pairs plants with their “friends.”
Companion planting is a technique used by gardeners for determining where plants should be placed in gardens. When specific plants are placed together there is a resulting synergistic effect. Companion garden plants often grow better, yield more or taste better. And because plant species are mixed together in these gardens, the design mimics nature more than, for example, vegetables planted in long rows.
On the other hand, some plants have poor relationships. They have a negative effect on each other and should not be planted in proximity. Asparagus, for example, does not perform well planted next to garlic or onions. And broccoli does not befriend snap beans or strawberries.
Companion planting is also employed as an organic method of pest and disease control. Certain plants are grown alongside crops to help reduce pest attacks. Strong-smelling herbs, such as mint and garlic, are often used in this manner. They repel the pests that are drawn to specific crops by their scent. How? Nearby scents confuse the pests’ sense of smell. Some companion plants sacrifice themselves rather than have adjacent buddies destroyed by pests. French marigolds, for example, are useful in ridding plants of aphids. The marigold flowers draw hoverflies, which produce larvae that feed on aphids.
Tomato family plants, which include tomatoes, potatoes, eggplants and peppers, do not fare well planted together. Tomatoes and potatoes grow well next to peppers and eggplants, but tomatoes and potatoes do not grow well next to each other. If in doubt, look it up! Lists of plant families, their friends and their adversaries are found on the Internet or consider reading books such as The Vegetable Gardener’s Bible by Edward C. Smith. Smith’s bible says that onions are beneficial to the mustard family because they deter moths. And it states that radish leaves draw flea beetles away from other crops while carrots benefit from being planting near rosemary or sage. Little science is offered in evidence for companion planting. However, the practice is explained in trusted reference books and on university Internet sites.
Resources: Rodale’s Encyclopedia of Herbs, American Horticultural Society, Vegetable Gardener’s Bible
Questions? Call AgriLife Extension 817-579-3280 and ask to speak to a Master Gardener.