Carrots Love Tomatoes: Companion Planting for a Healthy Garden

Image Gallery Cabbage is helped by aromatic plants such as celery, onion, sage or -- as pictured here -- marigolds. PHOTO: DAVID CAVAGNARO

The A to Z Guide to Companion Planting for Healthier Plants and Bigger Harvests  

The magic and mystery of companion planting has intrigued and fascinated man for centuries, yet it is a part of the gardening world that has never been fully explored. Plants that assist each other in growing well, that repel insects or that even repel other plants are all of great practical use. However, we’re just beginning to find out why, for example, carrots love tomatoes and radishes love lettuce. In the years to come, I hope scientists, gardeners and farmers everywhere will work together to make discoveries that will prove of great value in augmenting the world's food supply. Already, companion planting has produced insect- and disease-resistant fruits, grains and vegetables, and experiments are being conducted on weed-resistant varieties.  

A major enemy of the carrot is the carrot fly, whereas the leek suffers from the leek moth and the onion fly. Yet when the leek and the carrot live in companionship, the strong and strangely different smell of the partner plant repels the insects so well that they do not even attempt to lay their eggs on the neighbor plant. This is why mixed plantings give better insect control than a monoculture where many plants of the same type are planted together in row after row.  

It's the same with kohlrabi and radishes in their community life with lettuce. Both are often afflicted by earth flies, but when the flies get the odor of lettuce, they take off. Even when plants are affected by diseases, one can usually alleviate the situation with a mixed plant culture.  

All through this article, you will find "what to grow with" and "what not to grow with." Both are equally important to gardening success. The following suggestions for companion planting are only a beginning. Your own experiments will lead you toward many different pathways and discoveries.  

Asparagus (Asparagus officinalis). Parsley planted alongside asparagus gives added vigor to both. Asparagus also goes well with basil, which itself is a good companion for tomatoes. Tomatoes will protect asparagus against asparagus beetles because they contain a substance called solanine. But if asparagus beetles are present in great numbers, they will attract and be controlled by their natural predators, making spraying unnecessary. A chemical derived from asparagus juice also has been found effective on tomato plants as a killer of nematodes, including the root-knot sting, stubby root and meadow varieties.  

In my garden, I grow asparagus in a long row at one side. After the spears are harvested in early spring, I plant tomatoes on either side, and I find that both plants prosper from the association. Cultivating the tomatoes also stems weed growth around the asparagus. The asparagus fronds should not be cut much, if at all, until very late in the fall, as the roots need this top growth to enable them to make spears the following spring.