The practice of growing plants that may have a beneficial effect on their neighbors is called companion planting. Plants that repel pests or that attract pollinating insects make good companions for crops.
Keep companion plants 12-24in (30-60cm) extremely sticky and act as flypaper, from the main stems of tomato plants— close enough to be beneficial, without competing with the tomatoes for nutrients. In a greenhouse or polytunnel, place pots of companions among the crop.
Ideal plants to grow with tomatoes include basil, chives, onions, carrots, mint, and parsley. Marigolds, especially the French marigold (Tagetes patula), are thought to be particularly good at repelling whitefly (pp116-117) and even nematode pests that may be present in the soil. Marigolds are long-flowering plants and, like nasturtiums (Tropaeolum majus), will attract many pollinators. The beautiful, blue-flowered herb, borage (Borago officinalis), is said to deter moths that may damage tomato plants (pp116-117).
In greenhouses prone to infestations of whitefly or fungus gnats, it is worth growing a few plants of the common unicorn plant (Proboscidea louisianica), also known as the common devil's claw or elephant's tusk. This pretty plant with showy gloxinia-like flowers has oval, wavy-edged leaves that are covered in glandular hairs that sparkle in the light. The leaves are catching many small insects. The plant is considered a noxious weed in some US states because the strange, clawed seedpods can damage the eyes of livestock. Allow it only to set sufficient seed to grow a few new plants for the next year.
Mycorrhizae are soil-borne fungi that form symbiotic (mutually beneficial) relationships with plants. They colonize the roots of a nearby plant, such as a tomato, and extend their network (mycelium) of fine, sticky filaments, known as hyphae, into the nearby soil. A mycelium increases the surface area of the roots of a host plant, enabling the host to absorb more food and water. It is also thought that the sticky hyphae protect the plant from soil-borne fungal diseases, making it difficult for them to invade the host. Mycorrhizae thrive in rich, organic soils, but are destroyed by digging and the high salt content of chemical fertilizers, so organic cultivation methods are thought to be particularly beneficial.
Best friends (clockwise from top left) mint (Mentha), chives (Allium schoenoprasum), French marigolds, and nasturtium. >
Was this article helpful?
You Might Just End Up Spending More Time In Planning Your Greenhouse Than Your Home Don’t Blame Us If Your Wife Gets Mad. Don't Be A Conventional Greenhouse Dreamer! Come Out Of The Mould, Build Your Own And Let Your Greenhouse Give A Better Yield Than Any Other In Town! Discover How You Can Start Your Own Greenhouse With Healthier Plants… Anytime Of The Year!