We have some cabbage and kale growing and while some of them are growing well, others are getting eaten by pests. Rather than spray our plants, we wanted to see which companion plants can naturally repel the pests. So, I did some research. Here’s what I found.
The best companion plants for brassicas are alliums, rosemary, lavender, sage, and nasturtium. These plants are great at repelling many destructive brassica pests such as whiteflies, cabbage moths, and cabbage aphids. Nitrogen-fixing plants such as legumes are also good at planting before or around the brassicas.
So, while these are some of the best companions for brassicas, exactly which benefits do they bring, and what are some other companion plants? Let’s take a closer look.
Benefits of Companion Planting
Companion planting is selecting specific plants to place together to achieve benefits, such as increasing pollination or repelling pests. Sometimes these benefits are one-sided, while others are mutual.
A famous example is The Three Sisters—planting corn, beans, and squash together. The corn provides a trellis for the beans to climb, the squash provides a ground cover, and the beans fix nitrogen in the soil. Plus, all of them provide food!
Here’s a list of the benefits that gardens gain from companion planting:
- Boost Pollination
- Repel Pests
- Prevent Weeds
- Fix Nitrogen
- Amend the Soil
- Cover the Soil
- Reduce Evaporation
- Provide a Living Trellis
- Maximize Space
- Produce More Food
If you’d like to learn more about the benefits of companion planting, check out my other post: The Top 10 Benefits of Companion Planting.
What Are Brassicas?
Brassicas, also called cruciferous vegetables, are a genus of plants within the cabbage and mustard family.
Any brassica will benefit from the companion plants in this post. However, if you’d like, here’s a list containing the majority of brassica plants:
- Brussels Sprouts
- Bok Choy
Brassicas themselves generally don’t benefit many other plants as they’re primarily a vulnerable food crop, but they can provide a decent ground cover and habitat for beneficial insects and predators.
Now, let’s jump into the best companion plants for brassicas.
1. Alliums (Garlic, Onions, and Chives)
Alliums and brassicas are one of the best companion pairings largely because brassicas are fairly vulnerable to pests and disease.
For example, compared to growing rows of solely cabbage (aka monoculture), when onions and cabbage are interplanted, the onions repel many cabbage pests.
Significantly fewer Bemisia tabaci (whitefly), Hellula undalis (cabbage moth) and Brevicoryne brassicae (cabbage aphid) infested the intercropped plants than the sole crop.Canadian Center of Science and Education (CCSE)
And this isn’t true for just cabbages. Since brassicas are closely related, the same if not better results can be had with other brassicas.
Other pests can also be repelled by interplanting alliums with brassicas, such as aphids, mites, maggots, rabbits, and deer (source).
Additionally, it’s believed that the sulfur from these plants also helps prevent certain plant diseases to some extent. For example, a common companion plant pairing is interplanting chives near apple trees to prevent apple scab (source).
However, if fungal or bacterial diseases do take hold, garlic cloves can also be mixed into organic sprays along with neem oil and applied as a treatment.
Overall, you can plant any of these allium-family plants with just about any other plant, except for legumes.
2. Rosemary and Lavender
Since rosemary and lavender can grow into fairly tall bushes, it’s best to plant them a few feet away from your brassicas. As long as you plant them within 25 feet of your brassicas, you’ll get most, if not all of their benefits.
These herbs are is also super versatile in the home and kitchen. For example, we recently made this roasted leg of lamb the other night and it was SO good! This recipe used a lot of our rosemary, but it was some of the best lamb we’ve had.
You can also take cuttings of your rosemary and lavender plants, bundle them, tie them with twine, and hang them upside down to dry them out and store them for later. Rosemary in particular makes a great addition to many cabbage and veggie dishes.
Sage is native to the drier regions of the Southwest US (source). As a result, it’s a drought-tolerant plant. Additionally, you can use sage for some culinary, fragrance, and cleansing applications (such as burning sage).
Like rosemary and lavender, sage is known to repel pests such as snails, slugs, beetles (such as black flea), as well as cabbage moths (source). Flowering sage plants (such as purple sage) are well known for attracting pollinators.
Other companion flowering plants that also repel snails and slugs are strongly scented, aromatic plants including hydrangeas, California poppy, and nasturtium.
Sage pairs amazingly well with strawberries. Because of this, planting a combination such as sage, strawberries, and wildflowers makes a great pollinator and ground cover mix for most fruits, vegetables, and herbs.
Just make sure to keep the strawberries away from the brassicas as they can introduce Verticillium wilt. However, you can use other plants (such as sage) as a neutral barrier between these plants, along with other “foes”.
Some other companion plants that also pair well with sage include thyme, rosemary, and oregano. However, avoid planting sage near rue, cucumbers, or onions as they’re not compatible.
4. Cover Crops
Many legumes such as clover, peas, and runner beans (along with some grasses) are also called cover crops as they are great pioneer plants for depleted soils.
Cover crops are used to improve soil health by slowing erosion, retaining water, preventing weeds, and controlling pests and diseases. They’ve even been shown to increase crop yields.
In the drought of 2012, corn and soybean farmers reported a 9.6-11.6% yield increase when they used cover crops, likely due in part to the cover crop’s ability to add 50-150 pounds of nitrogen per acre.Source
These cover crops fix nitrogen in the soil by promoting beneficial bacteria which take nitrogen from the air and store it in the soil as nitrates for other plants to use (source).
And these benefits are just for corn and soy, but for other plants, including brassicas. Not only do brassicas prefer rich, healthy soil to grow, but the increased health from good soil helps them resist pests and diseases (and provide larger yields).
As many cover crops produce a lot of biomass, they can also be used to mulch brassicas for even more nitrogen and other nutrients (as well as reducing evaporation).
With cover crops such as clover, you can even grow them in-between your fruit trees and brassicas and run livestock through the alleys. Your livestock gets free food, many pests are deterred, and your brassicas get an amazing fertilizer in the form of manure (just make sure to protect your brassicas from your livestock!).
Most people I know have never heard of nasturtium, but when I show them a picture they quickly recognize it.
Nasturtium is often believed to be a weed, likely because it grows quickly and horizontally along the ground. However, because of this, nasturtium makes a great ground cover, reducing evaporation and protecting the soil from the elements and erosion.
Nasturtium’s edible flowers have nectar that’s sweeter than most others. This is because it’s made from highly concentrated sucrose instead of glucose or fructose. As a result, it’s a highly desirable plant for pollinators.
Another reason why it’s great at attracting pollinators is that its long flowers evolved alongside the hummingbird’s long tongue (source).
Aside from providing ground cover and pollination, nasturtium has another benefit in companion planting—it attracts pests such as aphids and cabbage worms away from other plants (source). In this way, you can think of nasturtium as a “trap” or “sacrifice” plant.
Nasturtium is pretty durable when it comes to pests, so you shouldn’t have to worry about this plant becoming damaged itself.
However, if your nasturtium starts to get overrun with pests, plant dill, calendula, and cosmos nearby. For more info about these companion plants and others that repel plant pests and diseases, check out my other post: 10+ Companion Plants That Prevent Pests and Diseases.
Nasturtium’s shallow roots also mean that it’s not difficult to remove if you decide to part ways with it.
Plant nasturtiums along with raspberry (and other fruiting plants), legumes, tomatoes, asparagus, and brassicas. Avoid planting nasturtiums with squash and other vining plants since they can easily get tangled and compete.
You can also check out more nasturtium companion plants.
So, if you’d like a ground cover that attracts many pollinators (especially hummingbirds), plant nasturtium!
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Marigolds are a well-known companion plant (especially for potatoes) as they help manage the soil-borne populations of nematodes. This is also true for brassicas.
These nematodes often afflict home gardens and have no available chemical pesticide. Luckily, marigolds, are natural repellents against nematodes because they produce a substance called alpha-terthienyl, which is deadly for the nematodes.
For this reason, marigolds have been used as a cover crop in India for many hundreds of years in areas where nematode populations are high.
Of course, since marigolds are flowering plants, their appearance and nectar also attract pollinators such as bees, butterflies, and hummingbirds, which all benefit brassicas.
Just make sure that you plant a true marigold from the genus Tagetes, not Calendula, which sometimes goes by the same common name. The LSU College of Agriculture recommends the ‘Tangerine’ variety.
Speaking of calendula, both calendula and cosmos are both flowering plants that attract beneficial insects like wasps and hoverflies. I know, I know—how can ANY wasps or flies be beneficial? Who would invite these “pests” into their garden?
However, some wasps, such as paper wasps, feed on caterpillars, which we know are all too often damaging to plants (especially brassicas). These wasps take the caterpillars back to their nest, where they feed them to their larvae (source).
But, like most balanced ecosystems, the wasps don’t consume all of the caterpillars, leaving just enough of them to prevent major plant damage and develop into butterflies—pollinating the garden.
So, it’s effectively a win-win. You get rid of the majority of the caterpillars, your garden gets butterflies, and the beneficial wasps get a snack.
Hoverflies are also beneficial as they prey on aphids, reducing their population to reasonable numbers as well. Additionally, many flies, including hoverflies, assist in pollination, although not as well as bees (source).
Small note: calendula is also called pot marigold, but it’s not the same as a traditional marigold. However, they are in the same family.
Chamomile is a great companion plant for brassicas because it’s easy to grow, fixes nitrogen in the soil, attracts beneficial insects, and grows well in partial shade.
There are two main types of chamomile: German (Maricaria recutita) and Roman (Anthemis nobilis). Both are beneficial to have as companion plants.
First, chamomile helps fix the nitrogen in the soil by promoting beneficial bacteria to store nitrates in the soil (similar to cover crops). Their flowers also attract beneficial insects such as hoverflies, ladybugs, beneficial wasps, and honey bees.
Along with hoverflies, ladybugs are a natural predator of aphids and will also help to keep their populations down. They also eat spider mites.
Chamomile also grows well with mint and basil. You can also make chamomile tea with its flowers. The more common variety to use for tea is Matricaria chamomilla.
To see more companion flowers, check out my other post: The Top 10 Companion Flowers for Gardens, Vegetables, & More.
Thyme is native to Eurasia, with a history dating back to 2750 BC—noting that thyme can be dried and mixed with pears, figs, and water for a topical medical paste (source). It’s also a great drought-tolerant plant.
Like just about all of the flowers on this list, thyme’s flowers and scent are incredibly useful at attracting pollinators, specifically honey bees. You can expect thyme to flower from May to September.
Similar to nasturtium, thyme is resistant and repels pests including cabbage worms, weevils, and cabbage loopers (source). It’s also said that thyme also reduces aphid populations by attracting ladybugs.
Of course, thyme has a lot of other uses. For example, at our home, we often use thyme in our bone broths and roasts. We’ve come to really appreciate thyme’s strong floral scent and taste.
Thyme is best planted with strawberries, brassicas, rosemary, and lavender. Avoid planting thyme near basil.
Like thyme, dill is another drought-tolerant herb, native to the Mediterranean, and is part of the parsley and celery family.
One of the most well-known companion qualities of dill is its ability to attract pollinators and beneficial insects such as ladybugs. So if your brassicas commonly get aphids, plant lots of dill!
You can also use dill in your garden to repel pests such as spider mites and cabbage loopers (source).
Plant dill with brassicas, lettuce, onions, corn, cucumbers, and fennel. However, avoid planting dill with carrots, caraway, and nightshade.
To see more companion herbs, check out my other post: The 10 Best Companion Herbs.
What Not To Plant With Brassicas
Avoid planting brassicas with nightshade, strawberries, asparagus, melons, squash, grapes, and radishes. While many of these plants will compete with brassicas for nutrients and sunlight, strawberries and nightshades (especially tomatoes and peppers) can introduce Verticillium wilt.