Companion planting is a horticultural strategy where different species are grown in proximity to enhance growth, deter pests, or maximize space efficiency. This practice is particularly beneficial for the cultivation of Brassica oleracea, commonly known as cabbage. Cabbage is a heavy feeder, requiring substantial soil nutrients, and is highly susceptible to infestation by specific insects. Selecting the correct plant neighbors can address these dual challenges, creating a more balanced and productive garden ecosystem.
Companions That Repel Pests
The primary threat to a developing cabbage head comes from pests that target the Brassica family, such as the cabbage white butterfly (cabbage worms) and the flea beetle. Gardeners combat these insects by planting aromatic herbs and alliums nearby. Strong scents from plants like sage, rosemary, and thyme confuse the adult moths, making it difficult for them to locate the host plant and lay eggs.
Alliums, including garlic, chives, and onions, function similarly, providing an olfactory barrier that deters pests like the cabbage maggot and aphids. Interplanting these slim, vertically growing crops directly between cabbage plants maximizes the repellent effect without competing for canopy space. This strategy exploits the insect’s reliance on scent to find its food source.
A different approach involves using a trap crop, which is a plant species more attractive to the pest than the main crop. Nasturtiums, for example, are highly favored by the cabbage white butterfly for egg-laying, drawing adults away from the cabbage. Planting certain mustard varieties near the cabbage patch can also lure pests like the cabbage worm, effectively sacrificing the decoy crop to protect the harvest. This method requires monitoring to ensure the trap crop is either removed or treated before pests complete their life cycle and move back to the cabbage.
Companions That Support Growth
Cabbage is a heavy feeder, demanding significant amounts of nitrogen for the development of its large head. Legumes such as bush beans and peas are excellent companions because they host Rhizobium bacteria in their root nodules. This bacteria fixes atmospheric nitrogen into a form available for plant use, providing a steady, organic source of the nutrient required for robust leaf growth.
Intercropping with plants that have different rooting depths and growth habits maximizes resource use and soil health. Shallow-rooted and quick-maturing crops like lettuce or radishes can be planted between cabbage plants. These utilize soil layers that the deeper cabbage roots do not reach, increasing the overall yield of the garden bed without compromising the cabbage’s growth.
Certain root vegetables, such as carrots, help to break up and aerate the soil as they grow, improving water penetration. Taller companion plants like beans can also provide necessary shade during the hottest parts of the day. This shade helps keep the soil around the cool-season cabbage plants from overheating and reduces moisture loss, mitigating heat stress that can cause the cabbage head to bolt prematurely.
Essential Plants to Avoid
While many plants offer symbiotic benefits, certain common garden vegetables and herbs should not be planted near cabbage due to direct competition or chemical inhibition. Tomatoes are an example of an incompatible plant, as they are heavy feeders that compete intensely with cabbage for soil nutrients. Tomato plants can also release substances that actively inhibit the growth of nearby brassicas, a phenomenon known as allelopathy.
Another category to avoid includes plants that share susceptibility to the same diseases or pests, which can accelerate the spread of infestation. Planting cabbage near other Brassica family members, such as broccoli or kale, creates a monoculture effect. This makes all the plants a more visible target for pests and diseases. Strawberries are also poor neighbors because they can serve as carriers for fungal diseases like fusarium wilt, which can easily transfer to the cabbage crop.
Plants with aggressive growth habits or allelopathic properties should be kept separate. Fennel is a well-documented example that releases chemical compounds that inhibit the growth of many other crops, including cabbage. Tall, vining plants like corn or pole beans can also be detrimental. They cast excessive shade over the low-growing cabbage, impeding the necessary sunlight for head formation and competing for ground-level resources.