Brassicas are members of the cabbage family. They can find a place in a polytunnel garden all year round. They often grow well with members of the same family. But growing them with other companion plants can help you to make the most of your crops Companion planting can be a great way to make the most of the space in your polytunnel and get the best possible yield. Here are some great companion plants for brassicas that you might like to consider:
Which Plants Are Brassicas?
Before we take a look at the best companion plants for brassicas, we should take a moment to discuss what exactly we means when we say ‘brassicas’. Members of the brassica or cabbage family include:
Broccoli and Calabrese
Choy Sum/ Chinese cabbages
All members of this plant family require similar conditions, and can often grow well together in the same growing area as long as their nutritional needs and environmental needs are met.
Other Vegetables That Are Good Companion Plants For Brassicas
Creating polycultures of edible plants is a great way to improve yield and enhance the biodiversity in your garden. Here are some other vegetables which can work well when planted alongside or between brassica plants:
Beans – Brassicas are leafy crops and, as such, need plenty of nitrogen to grow. Beans are nitrogen fixers and co-operate with bacteria on their roots to gather nitrogen from the air and make it available in the soil. Beans can be good to plant just before brassicas, but can also work well when grown alongside them.
Peas – Peas are another nitrogen fixer that can work well in a polyculture alongside your brassicas. Plant brassicas along the base of a row of peas and you can also take advantage of the shade the peas will provide as they climb during the summer months.
Potatoes – While you may not have the space to grow these in the same bed as your brassicas, they can do very well if planted relatively close to one another. Potatoes can have a detrimental effect when grown too close to a number of other plants. But broccoli and other brassicas can be good neighbours for your potato plants. They also tend to like relatively similar conditions.
Beetroot – Beetroots are a great crop to grow alongside your brassicas. They too like similar conditions and can work well when grown in the same area of your garden. Including beets in your brassica rotation plan could be a good idea, as long as you adhere to spacing requirements. Beets have low calcium requirements, and so can work well with broccoli and other brassicas which need plenty of calcium to thrive. Beets leaves, when dropped, put manganese and iron into the soil.
Celery – Celery’s long growing period means that it can be intercropped with brassicas successfully to make the most of the space available in your polytunnel. Some gardeners even swear that celery helps to improve the flavour of their brassicas when planted nearby.
Cucumber – While the reasons are not fully understood, some gardeners have also reported that they have had good results when growing their brassicas underneath their cucumber plants. Perhaps the cucumbers casting shade and improving the conditions in the summer months could be the reason.
Onions and Other Alliums – Onions and other alliums are great for repelling pests that often trouble brassica crops. So they can also be great companion plants for brassicas. Onion showed good resistance in trials to cabbage worm, weevil and cabbage looper.
Lettuce, Spinach (and other Quick Growing Leafy Greens) – Intercropping your slower growing brassicas with lettuce and other leafy greens can also be a great idea. Loose leaf lettuce and other quick crops can fill the gaps between your brassicas. They will be harvested before the space is required by these slower growing plants.
Herbs That Are Good Companion Plants For Brassicas
Brassicas also do better when planted alongside a range of different herbs. Aromatic herbs are beneficial to a range of brassicas, as they are for a range of other common garden crops. Here are some of the main herbs that have shown to be good companion plants for members of the cabbage family:
Rosemary – The strong aroma of rosemary can help to confuse pests that can decimate your brassica crop, such as cabbage white butterflies and moths. When rosemary is planted somewhere fairly close by, the cabbage smell will be masked and these lepidoptera are less likely to find them to lay their eggs.
Thyme – Thyme is another plant that can be a good companion for a wide range of crops. When planted close to brassicas, it is said to repel brassica pests such as cabbage root flies. Plant thyme near your brassica and you can also use it to make a tea that can be sprayed on the leaves of cabbages to prevent whitefly.
Marjoram – Marjoram is another great companion plant. Anecdotally, it is said to improve the flavour of almost any crop that is planted close by.
Dill – Dill is also said to improve the flavour of brassicas grown nearby, and is also said to stimulate the growth of plants in the cabbage family. This aromatic herb is also said to work to repel cabbage loopers.
Sage – The scent of sage is said to repel or distract a range of different brassica crop pests. As an aromatic herb it is a great companion for a wide range of different polytunnel crops.
Mint – There are a wide range of different mints that you can grow in your garden. Planting some mints close to your brassicas will allow them to exude their strong scent and repel, confuse or distract a wide range of pests that might plague members of the cabbage family.
Chamomile – The smell of chamomile is another plant which is said to repel a range of brassica pests. What is more, chamomile planted in your vegetable beds will also aid by bringing in pollinators.
Flowers That Are Good Companion Plants for Brassicas
Clover – Clover is a nitrogen fixing ground cover than may be beneficial for nitrogen fixation and ground cover when planted between or intercropped with your brassicas. When in flower, clovers can also help to draw in pollinators and other beneficial insects.
Lupin – Lupin is another interesting nitrogen fixing flowering plant that might work well intercropped with nitrogen-hungry brassicas. Lupins may also have potential as an edible pulse/ protein source.
Marigolds – Marigolds are an excellent companion plant and should be sown all around your vegetable garden. They release a chemical that kills nematodes. They also deter numerous other pests and attract pollinators.
Nasturtiums – Nasturiums may also be beneficial when planted close to your brassicas. They may help by drawing in beneficial insects, by acting as a trap crop, or by repelling or distracting a range of common brassica pest species. They can also shade the soil and reduce moisture loss to aid growing brassicas.
Borage – Borage is a dynamic accumulator, with deep roots that can bring nutrients from far below the ground. When chopped and dropped, these nutrients are returned to the soil surface, where they can bring benefits to brassicas grown nearby. When in flower, borage also attracts bees and other pollinators to your polytunnel.
Lavender – Lavender is another great plant for drawing in pollinators. So like other aromatic plants, it could be great planted around the edges of your brassica polyculture.
There are, of course, plenty of other beneficial combinations of plants that you could try. Companion planting is complex, and surprisingly poorly understood. Experimentation is key to finding the right polyculture combinations for your polytunnel garden. So simply give companion planting a go and note what works and does not work for you.
Bad Companion Plants For Brassicas
As you experiment, however, it is worth noting that certain plants are definitely not good companions for your brassica plants. For example:
pumpkins and squash
(These are all heavy feeders that will take nutrients away from brassicas, especially calcium.)
Also avoid planting brassicas with:
(These will attract verticillium wild which can damage brassicas.)
Many gardeners also report that radishes do not do well when planted near brassicas, and the brassicas will not enjoy the connection either.
Implementing the right polycultures and finding the right companion plants for brassicas can help boost productivity and reduce problems in your polytunnel.
What do you grow alongside your brassica crops? Share your experiences and suggestions in he comments below.
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.