Companion planting is defined as the close planting of different species based on their ability to enhance each plant's growth, offer some form of pest protection, or provide other advantages. Sometimes, this is a matter of choosing plants with different growth habits that do not 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 maintain. A cool-season vegetable, broccoli fully matures in 55 to 80 days from transplants, 100 to 150 days from seed. In areas where frost comes late, you can grow it in spring, and then plant it again for a fall crop.
Broccoli dislikes temperatures higher than 75°F, so midsummer is not the time for broccoli. It likes temperatures between 45 and 75°F, but it is frost tolerant and will even survive occasional temperatures down to 20°F. Although it likes full sun for at least six hours per day, broccoli is one of the few vegetables that will produce in partial shade. It prefers soil that's slightly acidic, with a pH of 6.0 to 6.5, and needs consistently moist, well-drained soil rich in organic matter. Broccoli is the perfect season-extender for early and late garden harvests.
Broccoli's Preferred Neighbors
Broccoli does not mind having most other vegetables as close neighbors, and it rarely hinders others in their growth. The exceptions are other plants with very heavy calcium needs, as broccoli does consume a lot of calcium from the soil (that is one of the nutrients 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.
Opinions are mixed on whether other members in the cabbage family are good companions for broccoli. On the one hand, all these plants have similar needs for nutrients and watering, which means that planting them close to one another should be an effective strategy. Other experts suggest that because many of the same pests feed on these plants, it's best to keep them apart in the garden in order to discourage mass insect attacks.
Potatoes can have a negative effect on the growth of many vegetables, but not so with broccoli, which seems unaffected by being in close proximity to potatoes.
In general, it is best to interplant broccoli with plants that do not need a lot of room and those that 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 and these recommendations are exactly the same for Brussels sprouts, too.
Plants That Help Broccoli Grow Better
Because broccoli is a notorious calcium-hog, plants that require little calcium are good companions, such as beets, nasturtiums, and marigolds.
Though the reasons are not well understood, some other plants that broccoli seems to enjoy as neighbors include:
Plants to Avoid Putting Near Broccoli
A few plants have the reputation for having a decidedly negative effect on the growth and flavor of broccoli. Beans, for example, tend to fix nitrogen in the soil, and the soil may be too rich for broccoli to tolerate. The rather short list of plants to avoid near broccoli include:
Some heavy-feeding plants are also not well suited for planting near broccoli, which is also a heavy feeder. For this reason, avoid these plants that will compete for nutrients in the soil:
"Calcium And Strong Bones". Physicians Committee For Responsible Medicine, https://www.pcrm.org/good-nutrition/nutrition-information/health-concerns-about-dairy/calcium-and-strong-bones.
Companion Planting: Anecdotal or Tried and Tested? University of Illinois Extension Service
Reinprecht, Yarmilla et al. "Effects Of Nitrogen Application On Nitrogen Fixation In Common Bean Production". Frontiers In Plant Science, 2020, https://www.frontiersin.org/articles/10.3389/fpls.2020.01172/full. Accessed 10 Aug 2021.