Companion planting can be defined as the close planting of different species based on their ability to enhance one another's growth or offer some form of pest protection or other advantages. Sometimes this is a matter of choosing plants with different growth habits that don't compete with one another or those that have different nutrient needs that make efficient use of soil. Strategic companion planting is especially important in small gardens or wherever careful space planning is needed.
Broccoli (Brassica oleracea) is a member of the cabbage family, along with cauliflower, Brussels sprouts, and collard greens. It is an excellent plant to grow, because not only is it one of the most nutritious of all vegetables, but it is fairly easy to grow and is not fussy. A cool season vegetable, it fully matures in only 6 to 8 weeks, and can then be cleared away to make room for a late summer/ fall crop. Or, you can plant it again for a fall crop in areas where the frost comes late. It dislikes temperatures higher than 75F., so the midsummer is not the time for broccoli. Although it likes full sun, it is one of the few vegetables that will produce decently in partial shade. And its soil needs are rather low-key; it does fairly well both in sandy soil and soils rich in clay--and everything in between. All told, broccoli is one of the more accommodating vegetables you can grow.
Broccoli doesn't mind having most other vegetables as close neighbors, and it rarely hinders others in their growth.
The exceptions are plants with very heavy calcium needs, as broccoli does consume a lot of calcium from the soil (that's one of the things that makes broccoli such a good health food). Broccoli growers may want to consider bone meal or another calcium-rich soil amendment to areas of the garden that are growing broccoli.
Potatoes can have a negative effect on many vegetables, but not so with broccoli, which seems unaffected by being in close proximity to potatoes.
In general, it's best to interplant broccoli with plants that don't need a lot of room and which enjoy some shade in the late spring and early summer when broccoli growth is most robust. Plants that fit this category include loose leaf lettuce, spinach, Swiss chard, and radishes.
Beyond that, the list of good neighbors for broccoli is a large one. (Note: these recommendations also hold true for Brussels sprouts, a close cousin of broccoli.)
Plants that Help Broccoli Grow Better
- Celery, potatoes, and onions improve the flavor of broccoli when planted nearby.
- Aromatic herbs, such as rosemary, sage, dill, and mint, help broccoli by repelling insect pests.
- Plants that require little calcium, such as beets, nasturtiums, and marigolds are good companions because they grow happily with broccoli--a notorious calcium-hog
Plants to Avoid Near Broccoli
Tomatoes, pole beans, lima beans, snap beans, squash, and strawberries are all said to negatively affect the growth and flavor of broccoli.