Kohlrabi Companion Plants | Friends and Foes

Kohlrabi (Brassica olearcea var. gongylodes) isn’t a vegetable found in every garden. Even the name sounds a bit foreign. In German, kohlrabi translates to ‘cabbage turnip’ — an apt description of this vegetable’s appearance.

Though somewhat rare and odd-looking, knowing that kohlrabi is closely related to fellow brassicas like cabbage and broccoli tells us a lot about its growing requirements. It also reveals which plants can be successfully grown in the same garden plot.

In this article, I’ll cover the best kohlrabi companion plants for pest control, disease management, and just a happier garden overall.

How Companion Planting Works

Companion planting, also known as interplanting or intercropping, uses the beneficial qualities of certain plants (such as the ability to deter harmful insects) to aid others growing in the same plot. This technique has been practiced for centuries, with the Three Sisters method being the most well-known historical example.

3 Ways Kohlrabi Companion Plants Are Beneficial

1. Pest Control

Kohlrabi is susceptible to common brassica pests. The worst culprits include cabbage worms, aphids, cutworms, flea beetles, diamondback moths, and cabbage loopers. 

diamondback moth caterpillar

One of the most effective (and most sustainable) ways to control these pests is to increase the number of predatory insects in your garden. You can do this by planting beneficial herbs and flowers that support the predatory insects’ various life stages.

Which Insects Help Control Kohlrabi Pests?

Tachinid flies are regarded as one of the most important predatory bugs in the gardening industry. There are several thousand tachinid species found throughout the world. Adult flies prey on the larval stages of cutworms and cabbage loopers.

Damsel bugs are generalized predators that feed on aphids, flea beetles, and the caterpillars of diamondback moths. Damsel bugs won’t harm the plants they live on and tend to leave more desirable insects alone.

Lacewings are another incredibly beneficial insect. Some species are even farmed commercially for targeted pest control on agricultural crops. Lacewing larvae feed on flea beetles, aphids, and caterpillars.

Parasitic wasps range in size and habitat, with the Trichogramma genus being one of the most impactful in terms of pest control. These wasps prey on the eggs, larvae, and adults of various pest species, including cutworms, cabbage worms, cabbage loopers, aphids, and flea beetles.

Hoverflies, also known as syrphid flies, are often mistaken for small bees or wasps. The larvae feed on pests like aphids and flea beetles. The adults primarily eat nectar and are significant pollinators.

2. Disease Management

Kohlrabi can suffer from diseases like clubroot, black rot, and bacterial soft rot. Effective companion planting can reduce the prevalence of these diseases. However, it’s more about knowing what NOT to plant than the other way around.

The most severe kohlrabi diseases tend to be those that specifically target brassica crops. Avoid planting all of your brassicas in the same plot. It’s also recommended not to plant any brassica in a given area of soil more than once every four years.

3. Shelter and Shade

Like other cool-season crops, kohlrabi likes to bolt in hot weather. Bolting is the premature development of a flower stalk that can interfere with flavor and texture. 

Basic cultural practices like timely planting and consistent watering can help prevent bolting. According to the University of Illinois, supplemental shade is also beneficial. You can use taller plants to create midday shade and ground cover to insulate the soil.

Best Vegetables, Herbs, and Flowers to Grow with Kohlrabi

Kohlrabi is a cool-season vegetable that produces a swollen stem (which looks and tastes a lot like a root vegetable). Most varieties are predominantly white, green, or purple.

This crop likes well-draining soil with a near-neutral pH. It responds well to a nitrogen-based fertilizer or aged compost applied early in the growing season.

Your kohlrabi will grow best in full sun — i.e., at least 6 hours per day — so be careful not to smother it with larger specimens. However, as I previously mentioned, a bit of midday shade can be very beneficial during hot weather.

You’ll want to select companion plants that share these growing requirements and that will help your kohlrabi stay as happy and healthy as possible until harvest time.

Vegetables

Beans: Beans and other legumes transfer nitrogen from the atmosphere into the soil. Kohlrabi needs a good amount of nitrogen during the growing season to thrive. I prefer bush beans because they’re less likely to choke out their neighbors.

Onions and Garlic: Onions, garlic, and other alliums may deter pests thanks to their strong odors. Research also shows that garlic can improve the availability of nutrients in some scenarios.

Beets: While harvested kohlrabi resembles a root, it is very different from actual root vegetables like beets. The reason beets make excellent companion plants for kohlrabi is that they do all of their work beneath the soil, well out of the way of the kohlrabi stems.

Potatoes: Potatoes are another good underground companion for kohlrabi plants. These two vegetables prefer very similar growing conditions and are fairly easy to cultivate together.

Lettuce: Similarly, head lettuce won’t compete with kohlrabi as long as the plants are placed far enough apart. Both lettuce and kohlrabi benefit from midday shade and cool soil, making them well-matched garden mates.

kohlrabi growing near lettuce

Radishes: Radishes mature quickly and can be tucked between more space-hungry vegetables throughout the garden. The leaves act as a trap crop, distracting flea beetles and cabbage worms from kohlrabi and other nearby brassicas. 

Peas: Peas are another type of legume worth adding to the garden to help replenish available nitrogen in the soil.

Carrot: Carrots and kohlrabi can be grown relatively close to each other without competing for resources. Allow a few carrot plants to flower each year (rather than harvesting the root) to attract hoverflies and tachinid flies.

Herbs

Dill: Dill attracts a variety of beneficial insects like hoverflies, tachinid flies, lacewings, and wasps. Note that dill doesn’t grow well with some of the other kohlrabi companions listed here, including carrots, cilantro, and potatoes.

Mint: Mint supposedly repels pests that dislike the herb’s strong aroma. Damsel bugs may use mint for shelter or as a food source. I recommend planting mint in individual containers to prevent it from spreading.

Rosemary: Rosemary is closely related to mint and offers many of the same pest-deterring benefits. Since rosemary can get quite bushy, it’s best planted near your kohlrabi but in a separate bed.

Thyme: Flowering thyme attracts bees and other pollinators, as well as predatory insects like the tachinid fly. Some gardeners claim that growing thyme near kohlrabi improves the latter’s flavor.

Parsley: Parsley is a versatile herb that attracts helpful predators like parasitic wasps and tachinid flies. It’s easy to grow and unlikely to compete with kohlrabi as long as the bed is kept well-watered.

Cilantro: Hoverflies love cilantro, especially when it’s in bloom. If space allows, you can also let your cilantro grow a bit wild to suppress pesky weeds.

Chamomile: Chamomile is an attractive herb that looks quite charming growing alongside kohlrabi. It also releases beneficial biochemicals into the surrounding soil which can improve the growth of nearby crops.

Flowering Ornamentals

Marigolds: Marigolds are often used to deter pests but they are much more effective at drawing beneficial insects like the damsel bug. Signet marigolds (Tagetes tenuifolia) appear to be the most attractive to these garden helpers.

Nasturtiums: These flowers are an extremely popular trap crop for aphids. The entire nasturtium plant is also edible, though most parts are used as garnishes rather than as the bulk of a dish.

 kohlrabi growing near nasturtium

Cosmos: Cosmos are tall, daisy-like flowers commonly used as colorful ornamentals. They’re quite effective at increasing the number of lacewings and damsel bugs who visit your garden.

Sweet Alyssum: Sweet alyssum is one of my favorite filler ornamentals. It’s a great ground cover for suppressing weeds and retaining soil moisture around kohlrabi. Planting sweet alyssum will also attract green lacewings and hoverflies.

Pansies: These cool-season flowers provide much-needed color during the spring and fall. Tachinid flies are particularly fond of pansies, so be sure to plant some near your kohlrabi plants.

Asters: Asters are daisy-like flowers belonging to the Symphyotrichum genus. They bloom later in the year than many other ornamentals, providing a valuable food source to tachinid flies, lacewings, and run-of-the-mill pollinators.

Coreopsis: Coreopsis plants also tend to have a long blooming period. Hoverflies and lacewings will pay these flowers a visit before tackling the pests on your kohlrabi.

Yarrow: Yarrow is a tough wildflower that attracts hoverflies and a whole host of other beneficial bugs. Its root system can take in nutrients from far below the soil’s surface, improving the topsoil over time.

Tansy: Tansy has distinctive clusters of small, yellow flowers. It attracts several predatory insects, including tachinid flies, hoverflies, and a few species of parasitic wasps. Note that tansy is toxic and may be invasive in some regions.

Rudbeckia: Also known as black-eyed Susan, this hardy perennial is easy to grow along the edge of a vegetable garden. The flowers are beloved by pollinators, hoverflies, and tachinid flies and the foliage may provide a bit of shade in summer.

Worst Companions for Kohlrabi

Kohlrabi should be planted away from other members of the brassica family, including cabbage, kale, broccoli, cauliflower, mustard, and turnips. These vegetables attract all of the same pests and diseases, so growing them together is a lot like installing a mini buffet for all of the bugs and pathogens in your garden.

Many gardeners advise against growing kohlrabi near tomatoes. The idea is that kohlrabi and tomato plants both take up a ton of resources from the soil and growing them in the same spot will lead to competition.

Melons and squashes also make poor bedfellows. In addition to competing for nutrients and water, these plants can quickly choke out kohlrabi with their vining growth habits and large leaves.

While strawberries are unlikely to choke out your kohlrabi, planting the two close together might increase the number of slugs and snails. If these pests are a known problem in your garden, I suggest being choosy about growing kohlrabi and strawberries at the same time.

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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.