The Brussels sprout is a cool-season vegetable prized for the miniature heads that develop along its tall, sturdy stem. These plants require a long growing season, often taking 80 to 100 days from transplanting to harvest, and are categorized as heavy feeders due to their high demand for soil nutrients to support their large structure and dense production. To sustain this demanding crop naturally, many gardeners employ companion planting, a technique that leverages the beneficial interactions between different plant species grown in close proximity. This strategy helps create a balanced garden ecosystem that supports the sprouts’ nutritional needs and defends them against common garden pressures.
Companion Plants for Pest Deterrence
A primary function of companion planting with Brussels sprouts is to confuse or repel the numerous insect pests that target the Brassica family, such as the cabbage worm, cabbage looper, and flea beetle. Aromatic herbs are highly effective because their strong volatile oils can mask the distinct scent of the sprouts, making it difficult for pests to locate their preferred host plants. Planting herbs like rosemary, dill, mint, and thyme nearby can disrupt the olfactory signals used by these insects.
The allium family, including garlic, onions, and chives, provides another layer of defense through the release of sulfur compounds. These potent compounds are responsible for the plants’ pungent aroma and act as a broad-spectrum repellent against pests like aphids and certain beetles. Low-growing alliums are particularly useful as they do not compete with the tall sprouts for sunlight.
Certain flowering plants serve as both repellents and trap crops in the garden. Nasturtiums, for example, possess a peppery scent that deters several brassica pests, but they also function as a desirable alternative host for aphids. By attracting aphids away from the sprouts, nasturtiums concentrate the pests in one area where they can be more easily managed or left to serve as a food source for beneficial insects. Similarly, fast-growing radishes can be used as a trap crop for flea beetles, whose preference for radish leaves distracts them from the Brussels sprouts foliage.
Other flowers, like marigolds, are reported to deter a range of pests, and when their foliage is tilled into the soil, they release a substance that can repel nematodes. Chamomile flowers attract beneficial insects, such as parasitic wasps and hoverflies, which prey on pest populations like cabbage loopers. Interplanting these flowers and herbs creates a diverse environment that makes it harder for pests to establish a foothold while simultaneously encouraging natural predators to remain in the garden.
Companions for Soil Enrichment and Support
Since Brussels sprouts are heavy feeders, companions that contribute to soil health and nutrient availability offer significant advantages to the crop’s long-term growth. Legumes, such as bush beans and clover, perform a process called nitrogen fixation, wherein beneficial bacteria in their root nodules convert atmospheric nitrogen into a form usable by plants. This natural nitrogen input is valuable for the sprouts, although gardeners must be mindful to maintain a balance, as excessive nitrogen can sometimes promote lush foliage at the expense of tight sprout development.
Root vegetables are beneficial because they occupy a different soil layer than the deep taproot of the Brussels sprout, minimizing direct competition for nutrients. Carrots and beets, for instance, help to loosen and aerate the soil as their roots grow, which improves water and nutrient penetration for the surrounding sprouts. Beets also contribute a boost of magnesium to the soil, a nutrient important for the successful growth of brassicas.
Low-growing vegetables and herbs can serve as a living mulch beneath the tall sprout stalks, helping to suppress weed growth and retain soil moisture. Spinach and lettuce are good choices because they thrive in the light shade provided by the mature sprouts. These plants have similar water requirements to the brassicas but utilize the space efficiently without competing for the same vertical growing area. Additionally, certain herbs, like thyme, are ground-hugging and can help suppress weeds around the base of the Brussels sprout plant.
Plants That Should Never Be Planted Near Brussels Sprouts
While some plants are helpful companions, others can actively harm Brussels sprouts through intense competition or by concentrating pest and disease issues. All plants within the Brassica family, including broccoli, cauliflower, and kale, should be avoided as immediate neighbors. These relatives are also heavy feeders, leading to direct competition for the substantial nitrogen and other resources needed to support the growth of the sprouts.
More significantly, all brassicas share susceptibility to the same pests and soil-borne diseases, such as clubroot and various fungal infections. Planting them together creates a monoculture that provides an easy pathway for diseases to spread rapidly, potentially leading to the loss of the entire crop. Introducing diversity by avoiding these closely related plants is a fundamental principle of garden health.
Other heavy feeders that require large amounts of nutrients and water, such as corn, tomatoes, peppers, and squash, should also be planted at a distance. Placing these high-demand plants near Brussels sprouts results in a nutrient tug-of-war, with both crops suffering from poor growth and reduced yields. Furthermore, some nightshade family members, like tomatoes, are susceptible to diseases that can also affect brassicas, increasing the risk of transmission. Strawberries are another incompatible neighbor, as they actively compete for the same space and nutrients, which can stunt the growth of the sprouts. Strategic garden planning that accounts for these negative interactions is an important step in ensuring a healthy and productive harvest.