Broccoli (Brassica oleracea) is a cruciferous vegetable that is rich in antioxidants. With lots of varieties to choose from, broccoli makes a delicious addition to many culinary dishes.
Although broccoli is slow growing, it’s hardy and one of the easiest crops to grow during the cool season. Like many edible plants, broccoli will benefit from companion planting, so long as you choose the correct partner plants.
Choosing the right companion plants can be somewhat challenging which is why I have written this article. It covers everything you need to know about companion planting to help you find the perfect partner for your broccoli plant.
What is Companion Planting?
Companion planting is the process of growing different plant species next to each other with the aim of providing benefits to at least one of the plants. There is a huge range of benefits that can be obtained from companion planting from increasing biodiversity to improving soil health.
Originally, this method of growing was used to grow crop plants as a way of enhancing their growth and yield. The success of this method has led to it becoming common practice in ornamental and landscaping gardens too.
Companion planting dates back thousands of years. First developed by Native American tribes, it has since been adopted worldwide. One of the oldest and most popular examples is called the “Three Sisters” method. It’s used to grow beans, squash and corn together.
Beans belong to a family of nitrogen-fixing plants called legumes. They take nitrogen from the air and convert it into a fixed compound in the soil. The squash and corn can take up this nitrogen and use it to aid their growth.
Squash has large, low-lying leaves which cast shade onto the soil. This helps retain moisture in the soil and also suppresses the growth of weeds that would otherwise compete with the crops for resources.
Corn acts as a natural support structure for the beans to climb up as it grows tall and sturdy. Likewise, the beans help to anchor the corn into the soil.
This example perfectly illustrates the role each crop plant plays in providing benefits to another.
Benefits of Companion Planting
When carried out with the correct pairings, companion plating can result in a wide variety of benefits. Some of the biggest advantages of companion planting with broccoli include:
Saves Space: Broccoli requires lots of growing space due to its large leaves. However, the idea behind companion planting is to grow plants close together. The right companions can be grown next to or amongst broccoli, saving soil space whilst allowing the plants to thrive.
Pest Control: Companion planting is a natural and organic growing method meaning chemical-based pesticides (and herbicides) are not used. Instead, this technique capitalizes on the natural pest-repelling properties many plants possess.
Growing companion plants that have strong scents, such as onions, can repel pests. As well as acting as a natural deterrent, their scent can also mask the fragrance of the main plant you wish to protect.
Eco-Friendly: Unlike monoculture, companion planting reflects the world’s natural ecosystems. It improves the biodiversity of both flora and fauna. Additionally, having plants close together creates a dense canopy. This provides shade and reduces evaporation which saves water.
Moreover, companion planting eliminates the need to use chemical-based pesticides and herbicides. As a result, you produce organic crops and do not pollute the environment or harm wildlife.
Attracts Beneficial Insects: Around 90% of the world’s crop plants are pollinated by insects. You can help attract pollinators to your crop by planting companions that are brightly colored or highly scented.
Some plants also attract predator insects such as ladybirds and hoverflies. These predators will feast on pest insects like aphids and whitefly, helping to protect your crop from infestations and damage.
Suppress Weeds: Low-lying plants or ones with large leaves are great at suppressing the growth of weeds. The dense canopy stops any weeds from growing through the soil which would otherwise compete with your crop for water and nutrients.
Considerations When Selecting Companion Plants
Clearly, companion planting provides a lot of benefits. However, there are considerations to think about when selecting plants you wish to grow together, as not every species makes for a great pairing.
Firstly, you need to understand the individual characteristics of your plants. For example, a plant that has a high moisture requirement would suffer if planted alongside one that requires little water. Fast-growing and deep-rooted plants are more likely to steal moisture from your crop.
Similarly, consider the soil conditions each plant flavors. If one species thrives in acidic soil but the other one needs alkaline soil, then they would make a poor partnership. Likewise, it’s a good idea to choose plants that have different nutrient requirements to reduce competition between them. Heavy feeders can rob nutrients from less aggressive companions.
With crop plants especially, it’s important to think about the growing space. Broccoli requires a lot of space but is slow growing. Make sure you leave enough space between companion plants so your crop can reach its maximum size and yield.
Many crop plant companions are chosen for their ability to control pests. These are called “trap crops” and draw the insects away from the crop you are trying to protect by attracting the pests to themselves. Think about what pests are attracted to what species and avoid grouping crops that are vulnerable to the same pests.
Good Companion Plants for Broccoli
Broccoli is fairly easy to grow and rewards you with a delicious crop that can be harvested between summer and autumn. It grows best in moist and fertile soil that is well-drained. Broccoli favours slightly acidic soil between pH 6.0 and 6.8.
You should plant broccoli in a location where it gets at least 6 hours of sunlight every day, otherwise, its growth and development will be inhibited. Like other members of the Brassicaceae family, broccoli is hardy and can be grown across USDA zones 2 to 11.
Some of the best companions for broccoli are those that require little space, repel pests and improve the flavour of this cruciferous vegetable. Such companions include:
Flowering Annuals and Perennials
Geranium: The delicate flowers of geraniums are great for adding a pop of color to your green broccoli patch. Additionally, they give off a pest-repelling scent.
Marigold: The fiery colors of marigold create a vibrant contrast against broccoli. They produce a scent which deters pests from your broccoli.
Snapdragon: The upright stance of Snapdragons is perfect for adding some height around your broccoli. Not only do the flowers create colour but also produce a scent that keeps insects away.
Beetroot: Broccoli requires lots of calcium whilst beetroot requires very little, meaning these vegetables won’t be competing for nutrients.
Celery: The flavor of broccoli can be improved by planting celery next to it.
Radish: Broccoli provides the radishes with shade and the radishes also take up little growing space.
Lettuce: Lettuce grows low to the ground and will help to shade the soil and keep it cool. Broccoli provides the lettuce with shade, which further helps to retain moisture in the soil.
Potato: Broccoli is one of the few vegetables that can be grown alongside potatoes. Both vegetables require lots of nutrients but have different needs so won’t be in competition with each other. Potatoes love phosphate and magnesium whilst broccoli loves nitrogen and calcium.
Rhubarb: Broccoli is susceptible to the cabbage whitefly which breeds on its leaves, making them inedible and damaging the crop. Rhubarb leaves contain toxic oxalic acid and release a smell which repels whiteflies.
Shallot: These vegetables take up less room than onions but are still known to improve the flavor of broccoli.
Spinach: When grown together broccoli and spinach work well as companion plants. Both sets of plants produce dark, leafy greens that grow low to the ground meaning they help to keep the soil cool. This also helps to prevent them from bolting upright and producing small leaves.
Chamomile: This herb gives off a lovely scent that attracts bees and other pollinators. Chamomile also helps to improve the flavor of broccoli and you can use this herb to make chamomile tea.
Rosemary: This hardy herb produces a fragrance that deters insect pests such as cabbage moths and cabbage loopers. Picking and scattering rosemary stems around your broccoli plants can also help keep slugs and snails away.
Thyme: The scent produced by thyme when used as a companion plant is excellent for repelling a variety of insect pests. Thyme also has a lot of uses in the kitchen.
Mint: The shade provided by broccoli will prevent the mint from growing too quickly and becoming invasive. The minty fragrance also keeps pests away from your broccoli.
Bad Broccoli Companion Plants
Some planting combinations can have negative effects on the health and growth of your broccoli. Some plants to avoid include:
Brassicas: Other members of this family include cabbage, cauliflower and Brussels sprouts. You should avoid pairing brassicas together because they will compete for the same nutrients and be susceptible to the same pests and diseases.
Heavy Feeders: Broccoli is a heavy feeder so you should avoid planting other heavy feeders nearby to avoid nutrient competition and deficiencies. Examples of heavy feeders include strawberries, sweetcorn and pumpkin.
Legumes: Beans, peas and lentils fix nitrogen into the soil from the atmosphere. Broccoli cannot tolerate a highly nitrogenous environment because it prevents the uptake of essential nutrients, resulting in stunted growth.
Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.