Mustard greens are a cool-season Brassica crop, favored for their spicy, peppery leaves and rapid growth. They thrive in moderate temperatures and are typically planted in early spring or late summer for a fall harvest. Companion planting involves placing different plant species near each other to create a mutually beneficial environment. This practice aims to improve the health and productivity of the main crop by utilizing natural plant interactions and maximizing garden space.
Strategic Allies: Plants That Enhance Growth
Maximizing the growth of mustard greens relies on mitigating heat stress and ensuring a steady supply of nutrients. Mustard greens are heavy feeders and require rich soil, especially nitrogen, to produce abundant, leafy growth. Planting legumes, such as peas or beans, nearby provides this necessary nitrogen through nitrogen fixation. These plants host Rhizobium bacteria, which convert atmospheric nitrogen into a form usable by plants, enriching the surrounding soil.
Mustard greens are prone to “bolting,” or prematurely going to seed, when temperatures rise above 75°F. Taller companion plants provide necessary shade to keep the soil and the greens cool during warmer parts of the day. Corn is an excellent structural companion because it grows upward without competing for the same root space as the low-growing mustard greens. The corn stalks create dappled shade, which prevents the mustard leaves from developing a bitter flavor and slows the bolting process.
Other low-growing crops, like spinach or lettuce, share the same cool-season growing window as mustard greens. When planted around the mustard, they act as a living mulch, covering the soil and reducing water evaporation. This ground cover also suppresses weeds that compete with the mustard greens for water and nutrients. Root vegetables like carrots are also helpful because their deep roots break up the soil, improving aeration and drainage, which benefits the mustard’s shallower root system.
Natural Pest Deterrents
Many common garden pests, including flea beetles, aphids, and cabbage worms, are highly attracted to mustard greens. Companion plants used for pest management rely on strong scents to confuse these insect pests or act as a distraction. Alliums, such as garlic, onions, and chives, release pungent compounds that mask the attractive scent of the mustard greens. This scent confusion makes it more difficult for pests like flea beetles and cabbage worms to locate the host crop.
Aromatic herbs like dill, rosemary, and mint also deter pests by releasing strong fragrances. Dill and chamomile are particularly useful because they attract beneficial insects, such as ladybugs and hoverflies, whose larvae prey on soft-bodied pests like aphids. Mint is a highly effective natural insect repellent against flea beetles and cabbage loopers, but it must be planted in a contained space to prevent its aggressive spread.
Another strategy is using “trap crops,” which are plants intentionally grown to lure pests away from the main vegetable crop. Nasturtiums are a classic example, as they are highly appealing to aphids and flea beetles. Pests will congregate on the nasturtiums, leaving the mustard greens relatively untouched and allowing the gardener to manage the infestation on the sacrificial plant. Marigolds also release compounds into the soil that deter nematodes, which are microscopic roundworms that damage plant roots.
Antagonists: Plants to Keep Far Away
Certain plants should be avoided near mustard greens because they create competition or increase the risk of infestation. Other plants within the Brassica family, such as kale, cabbage, broccoli, and cauliflower, should not be planted in close proximity. These plants share the same pest and disease vulnerabilities as mustard greens, attracting the same concentration of cabbage worms and flea beetles. Planting them together creates a large target for these pests, increasing the severity of any potential outbreak.
Plants that are heavy feeders or have a dense, shallow root system can aggressively compete with mustard greens for nutrients and water. Strawberries are one example, as they compete for the same resources and can inhibit the growth of the greens. Similarly, while alliums are generally beneficial, large, fast-growing onion plants can compete for nutrients and space, potentially stunting the mustard’s development.
Some plants produce allelopathic chemicals, which are natural compounds that inhibit the growth of neighboring plants. While black mustard (Brassica nigra) itself can be allelopathic, planting any known combative species nearby can negatively affect the leafy crop. The core principle is to avoid planting any species that forces direct competition for the nitrogen, moisture, and root space the mustard greens need to flourish.