Ask a Master Gardener:Do You Have BFFs in Your Garden?

By: Barbara Boone, Mobile County Master Gardener, www.mobilecountymastergardeners.org 

Many of us humans have friends we put in the BFF “Best Friend Forever” category, but did you know that plants can also have a BFF relationship with other plants? This association is called companion planting or interplanting.

Companion planting is all about growing edibles or non-edibles together, boosting plant health and reducing potential problems with pests and disease. When the main vegetable, herb, or flower is grown alongside a designated companion in healthy soil, they often grow better with fewer issues and less need for chemical intervention, especially if both plants have the same growth requirements such as watering and fertilization. In simpler terms, companion planting is identifying mutually beneficial plants and growing them together, a win-win in your garden.

A classic example is the “Three Sisters” planted by indigenous peoples where corn, beans, and squash were grown together. Corn supplied the structure, the beans supplied nitrogen, and the squash choked out weeds, altogether a mutual and beneficial relationship. Some gardeners still practice this today.

Companions help each other in the following ways:

·         Fix nitrogen in the soil with Rhizobium spp., pulling nitrogen out of the air and turning it into fertilizer.

·         Deter common pests.

·         Practice trap cropping where pests are lured away from the prized plant by offering an attractive alternative, a form of plant trickery.

·         Attract beneficial insects which eliminate pests.

·         Attract pollinators.

·         Suppress weeds.

The following are common examples of companion planting:

·         Tomato companions are basil, chili peppers, dill, onions, marigolds, and zinnias.

·         Strawberries pair well with beans, onions, spinach, and thyme.

·         Bell peppers grow well in the presence of hot chilis and herbs such as basil and cilantro.

·         Brassicas (cruciferous vegetables such as cabbage, broccoli, Brussel sprouts, cauliflower, turnips) do well planted near beans, onions, celery, dill, rosemary, sage, and zinnias.

·         Cucumber companions include beans, peas, sunflowers, and brassicas.

·         Carrot companions include beans, onions, peas, rosemary, sage, and geraniums.

Note that not all companions are vegetables. Herbs and flowers provide scents which many insects do not like and shy away from. Note also that companion planting is not an exact science and sometimes requires trial and error.

Having indicated many beneficial companions, there are certain plants that should NOT be planted in close proximity and do not make good neighbors:

·         Brassicas and strawberries are not good friends since brassica-loving insects are not picky and will infest the berries.

·         Cucumber and sage do not get along because the herb inhibits the vines, and each plant has different watering needs.

·         Beans and peas don’t do well in the presence of alliums (onions and garlic) mainly because alliums have antibacterial properties which may inhibit the aforementioned Rhizobium bacteria.

·         Corn and tomatoes both make tasty side dishes, but they are not good partners in the garden. Both are susceptible to corn earworms and both are heavy feeders requiring large amounts of nutrients leading to competition in the soil.

·         Potatoes and tomatoes are both members of the nightshade family and are susceptible to many of the same pests, and in addition are heavy feeders, again competing for many of the same nutrients.

Eggplant planted with marigolds. Photo by Mary Townsley