Broccoli and Brussels sprouts are both members of the Brassica family, commonly known as cole crops. This close botanical relationship means they share nearly identical fundamental biological needs, making them compatible garden neighbors. Therefore, the direct answer to whether you can plant them together is yes, provided you manage their high demands and unique growth patterns.
Shared Growing Requirements
The feasibility of planting these two crops together stems from their shared preferences for specific environmental conditions. Both are cool-weather vegetables that thrive when daytime temperatures range between 65 and 80 degrees Fahrenheit. They require full sunlight, meaning a minimum of six to eight hours of direct sun exposure daily.
A well-drained, moist, and fertile soil is a shared necessity, with loams and clay loams being ideal due to their high organic matter content. Soil structure must allow for efficient drainage, as waterlogged conditions are detrimental to the roots of both plants. The optimal pH range is 6.0 to 7.0, which helps maximize nutrient availability. These plants require a high and constant moisture supply, needing about one to two inches of water per week.
Spatial Arrangement and Resource Management
While their environmental needs align, the physical size and nutrient requirements of broccoli and Brussels sprouts make competition a challenge when planted closely. Both are heavy feeders, requiring significant amounts of nitrogen, phosphorus, and potassium throughout their long growing season. Nitrogen demand is especially high, as this element drives the leafy growth that produces the harvestable parts.
To mitigate nutrient depletion, a staggered approach to fertilization is necessary, often involving a side dressing of a nitrogen-rich fertilizer monthly after the plants establish themselves. Both plants are sensitive to micronutrient deficiencies, particularly boron, which is required for healthy cell wall development. The physical size difference also dictates careful spacing.
Brussels sprouts require significantly more space, needing plants spaced about 18 inches apart, with rows at least 36 inches apart. Broccoli is more compact and can be planted 8 to 12 inches apart, depending on the variety. Strategic placement of the bushier broccoli to the north of the taller Brussels sprouts helps ensure both plants receive adequate light.
Concentrated Pest and Disease Vulnerability
The most significant drawback to planting broccoli and Brussels sprouts together is the concentration of shared vulnerabilities to pests and diseases. Since both are members of the Brassica oleracea species, they attract the same insect pests and are susceptible to the same pathogens. This creates a monoculture risk where an infection can rapidly spread and potentially wipe out the entire crop.
Common insect pests that target both plants include the cabbage worm (the larval stage of the cabbage white butterfly), flea beetles, and aphids. The shared susceptibility extends to soil-borne diseases such as clubroot, which thrives in acidic soil, and black rot, a bacterial disease that causes yellow, V-shaped lesions on leaves. Physical barriers like fine mesh netting or row covers can prevent pests from accessing the plants.
Planting disease-free transplants and practicing a rotation schedule that avoids planting any Brassica crop in the same location for at least three years are necessary preventative measures.