Companion planting is the agricultural practice of placing different crops in proximity for mutual benefit, including pest control, nutrient sharing, and maximizing garden space. Turnips, a cool-season root vegetable, benefit from strategic partners that optimize the environment for healthy root and foliage growth. Selecting complementary neighbors enhances yield, reduces maintenance, and builds a more resilient garden ecosystem by minimizing competition and offering functional support.
Root-Friendly Neighbors for Shared Beds
Plants that share the physical growing space well with turnips typically possess different root depths or growth habits, preventing direct competition for resources. Leafy greens like lettuce, spinach, and Swiss chard are excellent neighbors because they are shallow-rooted and primarily absorb nutrients from the topsoil layer. This leaves the deeper soil available for the turnip’s developing taproot. Planting these greens between rows also provides a living mulch, shading the soil to keep it cool and moist, which prevents turnip roots from becoming woody or bitter.
Legumes, such as bush beans and peas, are beneficial partners because they fix atmospheric nitrogen into the soil through a symbiotic relationship with Rhizobium bacteria in their root nodules. Turnips require moderate nitrogen for healthy leaf growth and utilize this available nutrient source for improved vigor and root sizing. Bush varieties of beans are preferred over pole beans due to their compact growth habit, ensuring they do not overly shade the turnip foliage.
Fast-maturing root vegetables, particularly radishes, can be intercropped directly within the turnip rows. Radishes mature in three to four weeks, meaning they are harvested long before they compete significantly with the slower-growing turnips. This technique maximizes garden space by allowing for two harvests from the same area within a short period. Additionally, radish taproots help break up heavier soil, which benefits the subsequent turnip growth.
Functional Allies for Pest Management
Certain plants protect turnips from common pests like the flea beetle, cabbage maggot, and aphids, often through strong aromatic compounds. Aromatic herbs, including mint, rosemary, and thyme, can be planted along the borders to mask the smell of the turnips. This confuses pests that rely on scent to locate host plants. Mint, known to deter flea beetles, should be contained in a pot sunk into the ground to prevent its aggressive spread.
Alliums like garlic and onions are effective functional allies, emitting sulfur compounds that repel various insects, including aphids and root maggots, which attack the turnip roots. These compounds create an olfactory barrier that disrupts the pest life cycle. Planting a border of French marigolds helps control soil-dwelling pests; their roots release a chemical called alpha-terthienyl, which deters certain nematodes.
Nasturtiums function as a classic “trap crop” for aphids, luring the insects away from the turnips due to their strong preference for the nasturtium foliage. By concentrating the pests on a plant that is not the main crop, the gardener can monitor and manage the infestation more easily, thus protecting the turnips. The bright flowers of nasturtiums and dill also attract beneficial insects, such as ladybugs and parasitic wasps, which prey on turnip-damaging pests.
Antagonistic Plants to Avoid
Gardeners should avoid planting turnips near species that actively hinder their growth or invite problems. All other members of the Brassica family—such as cabbage, broccoli, cauliflower, and kale—are poor companions. They share the same nutrient requirements and are susceptible to the same pests and diseases, including clubroot and the cabbage worm. Planting turnips near these relatives creates a monoculture effect, leading to a rapid buildup and spread of pests.
Potatoes are also antagonistic due to their heavy feeding habits and dense, shallow root systems. They directly compete with the turnip’s developing root for moisture and nutrients, which can significantly stunt turnip growth. Furthermore, potatoes and turnips are vulnerable to some of the same soil-borne diseases, increasing the risk of crop failure.
Fennel is strongly allelopathic, meaning it releases chemical compounds, such as anethole, from its roots that actively inhibit the growth of nearly all nearby plants, including turnips. This growth-suppressing effect leads to stunted seedlings and poor root formation, making it a plant that must be isolated entirely from the vegetable garden.