Companion Planting for Broccoli
This cool-season crop attracts just as many gardeners as it does pests. Learn some companion planting techniques to ease the pest pressure on your precious broccoli crop.
Crunchy, tender, a bit sweet — broccoli florets picked fresh from the garden are a delicious treat. Delectable as garden-grown broccoli can be, battling caterpillars, harlequin bugs, aphids, flea beetles and myriad other pests can take the fun out of growing broccoli. Try companion planting to spend less time fighting bugs and more time enjoying the garden and harvest.
What is Companion Planting?
When paired with broccoli, some species of plants can discourage pests, attract predators to eat pests, suppress weeds or improve soil health (among other benefits).
"Trap cropping" is a method of companion planting in which plants beloved by pests are planted sacrificially — the idea is that the pests go for these crops over others. Trap crops are preferred by pests and can be used to lure pests away from broccoli plants. Trap crops for less mobile pests (like crucifer flea beetles) can be interplanted among broccoli plants, while traps for pests that can travel farther (like harlequin bugs) should be planted several feet away.
Many major broccoli pests hone in on the crop with their vision or smell, so several of broccoli's companions work by camouflaging it from pests. Some companion plants physically hide broccoli, while others mask plants with their fragrance.
To Discourage Caterpillars
Several species of butterflies and moths love to lay their eggs on cruciferous crops like broccoli. After the eggs hatch, the very hungry caterpillars of cabbage loopers, cabbageworms and diamondback moths can cause a lot of damage by feeding on leaves and flower buds.
- Underplant with thyme or a living mulch of white or subterranean clover to discourage cabbageworm butterflies or cabbage looper moths from laying eggs on broccoli.
- Plant annual herbs German chamomile or dill or perennial sage or hyssop to deter caterpillars. In her book Plant Partners: Science-Based Companion Planting Strategies for the Vegetable Garden, Jessica Walliser recommends planting with annuals to make crop rotation easier as relocating perennials like sage and hyssop can be a chore.
- Grow a plot of collards several feet away to lure diamondback moths from broccoli and other cruciferous crops.
To Discourage Flea Beetles
Crucifer flea beetles eat small holes in the leaves of broccoli and broccoli's relatives. Mature plants can handle some damage caused by these small black beetles, but an infestation can be devastating to seedlings.
- Interplant with fava bean, common vetch or white clover to make broccoli harder for flea beetles to find.
- If you have struggled with flea beetles in the past, grow a crop of radish, pak choi or Chinese mustard greens early in the growing season. Design your garden with alternating rows of broccoli and the trap crop for best results.
- Plant a combination of Pacific Gold mustard, canola and pak choi together as a trap crop. You may still notice some flea beetles in the garden but they will be more attracted to the blend of trap crops than the broccoli plants.
To Discourage Cabbage Root Flies
Cabbage root flies lay their eggs at the base of broccoli stems right at the soil line. After the eggs hatch, cabbage root maggots move down into the soil to feed on plant roots. Although mature plants can handle some feeding, the small white maggots can wipe out seedlings and transplants. The best way to prevent damage is to stop flies from laying eggs in the first place.
- Interplant with lettuce, beans or white clover to discourage cabbage root flies from laying their eggs.
- Companion plant with marigolds or onions to mask the smell of broccoli from the flies.
To Discourage Cabbage Aphids
Aphids are voracious sap suckers and prolific spreaders. In fact, they can even reproduce asexually without mating. These small green, grey or white insects prefer to eat succulent new growth, which can stunt plants and cause yellowed or wrinkled leaves.
- Cabbage aphids hone in on the crops by recognizing the contrast between the crops and the bare soil in the background. So, plant companion species closely (or even allow some weeds to continue growing) to hide your broccoli crops from aphids.
- Companion plant with mustard to camouflage broccoli both visually and aromatically from aphids.
To Discourage Harlequin Bugs
While many pests use camouflage to hide in the garden, harlequin bugs are certainly eye catching. These members of the stink bug family are fiery red with black spots, which stand out sharply against blue-green broccoli foliage. Although the adults and nymphs are flashy and relatively easy to spot, the eggs are often found under leaves. Look for clusters of eggs that resemble small black and white barrels. Harlequin bugs pierce broccoli plants to suck sap from the leaves and stems.
- Grow a plot of mustard greens (Plant Partners author Jessica Walliser recommends 'Southern Giant Curled') to lure harlequin bugs away from broccoli plants. Harlequin bugs are mobile and prolific, so plant the mustard greens several feet away and consider destroying eggs and collecting insects before they are able to reproduce.
To Attract Predators
- Grow lacy phacelia as a nectar source for beneficial insects, including parasitic wasps, tachinid flies and syrphid flies that eat pests of broccoli and its relatives. Other predatory insects like soldier bugs and miniature pirate bugs live on lacy phacelia as well.
- Companion plant with mustard and allow it to bloom (or "bolt") because its flowers attract predatory syrphid flies and parasitic wasps. To limit competition between the crops, hold off on sowing mustard seed until the broccoli has at least one week to establish.
- Grow flowering plants in the aster family (including cosmos, black-eyed Susan, sunflowers, daisies and zinnias) to support beneficial insects that prey upon aphids and other pests.
- Grow broccoli with crimson or white clover to provide habitat for pest-eating spiders. Hunting spiders feed on a variety of broccoli-eating insects, including caterpillars, beetle larvae and aphids.
Cosmos are an attractive and pollinator-friendly plant that can be useful in the vegetable garden, including as a companion for broccoli. Just be aware that they re-seed readily.
To Camouflage Your Crop/Cover Bare Soil
Mulching is a good practice to build soil quality, retain moisture and decrease weed pressures. Mulching brassicas like broccoli may decrease pest pressures, too. Straw, manure or compost as a mulch can provide habitat for predators of some cruciferous pests or limit pest movement.
- A living mulch of subterranean or white clover can suppress weeds without strongly competing with broccoli for resources like light and nutrients. In Plant Partners, Jessica Walliser cautions against planting crops from seed directly into subterranean clover due to its chemical ability to suppress seed growth.
Bad Neighbors for Broccoli
Annual flowers cleome, nasturtium, sweet alyssum and stock, as well as common garden weeds such as bittercress, watercress, pepperweed and shepherd's purse, can harbor broccoli pests.
Tips for Growing Broccoli
Hortus, Ltd./P. Allen Smith
In this garden grown using the square-foot-gardening technique, broccoli grows alongside lettuce, onions, cabbage and kale.
Broccoli is a cool season vegetable that grows best between 60- and 75-degrees, although it can tolerate cooler temperatures. Depending on where you live, spring, winter and fall are when broccoli will be the most productive. Look for varieties that will perform best in your region. Familiar heading broccoli is usually grown, although spear-forming broccoli raab is becoming more popular. Broccoli heads may be purple, yellow, or the traditional green.
Although you can sow broccoli seeds directly in the garden to start a spring crop, it can be better to start seeds indoors four to six weeks before the last frost. Check with your state or county extension service to learn when the last frost typically falls in your area. Broccoli seedlings need plenty of light while they are growing indoors, so place them by a window or under a light. Remember to acclimate seedlings by slowly introducing them to the outdoors before planting out. Broccoli seedlings can also be purchased from a local garden center.
Broccoli needs at least 6 hours of sun a day to grow best. Broccoli prefers rich, moist, well-drained soil. Mix in a healthy dose of compost to add organic matter, increase water holding capacity and improve drainage. Spread an organic mulch or plant a living mulch to help reduce weed pressures and provide an environment for predator species.
Harvest broccoli when the head is firm before the yellow flowers open. When the head (or spears in the case of broccoli raab) is ready to harvest, make a clean cut below the head rather than removing the entire plant. Once the head is removed, smaller side shoots will develop for another harvest. The general rule of thumb is the more you pick, the more shoots that will develop.