Harmful Companion Plants for Broccoli

Harmful Companions

• Along with other members of the cabbage family, broccoli is believed to harm, and be harmed by, tomatoes (Solanum spp.), which release a chemical from their roots that stunt growth. The High Plains Food Bank reports that some gardeners disagree about whether strawberries (Fragaria × ananassa) are harmful or helpful. Sustainable Gardening Australia claims that garlic (Allium sativum) and rue (Ruta graveolens) also stunt growth. Decomposing broccoli left in the soil can have a toxic effect on lettuce seedlings and may harm other cruciferous vegetables.

Cruciferous Weeds

• Cruciferous weeds can harbor black rot, a serious bacterial disease that only attacks members of the crucifer family. Black rot causes leaf yellowing, reduced plant vigor and dark, sunken lesions on vegetables. If left to grow nearby, wild cruciferous weeds can infect desirable cruciferous crops such as broccoli, cabbage and cauliflower, according to Cornell University. Cruciferous weeds include wild mustards such as Indian mustard (Brassica juncea) and black mustard (Brassica nigra) as well as weeds such as shepherdspurse (Capsella bursa-pastoris) and hairy whitetop (Cardaria pubescens).

Helpful Companions

• Luckily, more crops are helpful to broccoli than harmful. The High Plains Food Bank states that potatoes (Solanum tuberosum), onions (Allium spp.) and celery (Apium graveolens var. dulce) all improve the flavor of broccoli, while aromatic herbs such as dill (Anethum graveolens), peppermint (Mentha × piperita), sage (Salvia officinalis) and rosemary (Rosmarinus officinalis) help discourage pests. Broccoli is a bit of a nutrient hog that stockpiles calcium from the soil. Because of this, broccoli should be planted with plants that have low calcium requirements, such as beets (Beta vulgaris) and marigolds (Tagetes spp.).

Diversity

• Plant diversity is one of the foundations of companion planting. Planting lots of different species and varieties of plants helps to keep pests and diseases from wreaking havoc in the garden: If some plants are damaged by pests and diseases, others may survive because they are less susceptible genetically. Growing a selection of flowering plants along with your crops provides food and hiding places for pollinators and beneficial insects that will eat or parasitize crop pests.