How to Plant, Grow, and Care for Kohlrabi

Kohlrabi is a member of the cabbage family. The name Kohlrabi comes from two German words: Kohl and Rube. While kohl means cabbage, rube means turnip. So the name literally means “cabbage turnip” in German! Today, we’ll be discussing growing this vegetable in your own garden.

Kohlrabi originated in northwestern Europe. Today, this odd-looking vegetable is found worldwide. It is cultivated as a food source rich in vitamin C and vitamin B. It’s also an excellent source of minerals, especially copper, magnesium, potassium, and calcium. The calorie count is low, with only 27 calories per 100g of raw vegetable.

Fresh, young kohlrabi has a sweet taste and a juicy, crispy texture. The flavor profile resembles a mix of cabbage and radish. The bulb, stalks, and leaves can all be eaten, but the skin is a bit tough and is generally removed. It can be eaten raw or used in salads, soups, or meat dishes.

This alien, bizarre vegetable may not resemble anything we usually eat, but that’s part of its charm. Whether ‘Early White Vienna’, green, or purple kohlrabi (like ‘Early Purple Vienna’), it’s an unusual addition to your garden beds… and a delicious one, too. So, let’s talk about how to grow kohlrabi so you can enjoy this brassica in your garden and kitchen!

What is Kohlrabi?

The botanical name of kohlrabi is Brassica oleracea, and it’s part of the Gongylodes group and the cabbage family. If that seems like a mouthful, you can just call it by its common name, kohlrabi. It has a myriad of names in other languages, from su hào in northern Japan to kedluben in the Czech Republic. While the names are unusual, so is the vegetable itself!

Native Area

Brassica oleracea var. gongylodes is native to Europe, particularly the Mediterranean region, where it was developed from wild cabbage. It is believed to have originated in the 16th century as a cultivated variety of the same species that includes cabbage, broccoli, and kale. Kohlrabi thrives in temperate climates and has since spread globally, becoming especially popular in Europe, North America, and parts of Asia.

Characteristics

What does a kohlrabi look like? It has a broad, roundish bulb with protruding stems. These stems reach anywhere from six to eighteen inches tall, depending on the variety (unless we’re talking about giant varieties). Big, cabbage-like leaves with long petioles and wavy edges top each stem. The vegetable also produces flowers that are white or yellow and bloom in clusters on top of flowering stalks.

Varieties

Kohlrabi is not a root vegetable, as all portions are edible, but the bulb is most commonly used in food. The main producing countries include Russia, China, India, and Korea. If you’re looking to grow kohlrabi in your vegetable garden, select from varieties such as ‘Early White Vienna’, ‘Grand Duke’, ‘Gigante’ or ‘Superschmelz’, ‘Purple Kohlrabi’, and ‘White Danube’. They all vary slightly in exterior color, but the interior flesh is white for all kohlrabi varieties.

Planting

Kohlrabi does well in cool weather conditions. The best time to sow seeds is three to four weeks before the predicted date of the last spring frost, or earlier if you plan to start seeds indoors. These vegetables take 45 to 70 days to mature. As kohlrabi can survive an early frost, warm-climate dwellers can sow seed for a summer or early fall crop in the cool weather of autumn. Warm locations, such as southern California, can also grow it for a winter harvest.

Sow seeds directly in the ground or start seeds indoors. Live kohlrabi should be transplanted into the garden a little before the final frost date, so begin hardening them off to the outdoor temperatures in advance. Your seedlings should be four to six weeks old at the time of transplant for best success.

While kohlrabi can be grown in containers, it may require more frequent watering and fertilization. We recommend growing in raised beds with fertile, well-draining soil.

Space seedlings one to twelve inches apart in rows spaced at least the same distance apart. However, square-foot gardeners have been known to use intensive kohlrabi spacing, with as many as nine per square foot. This usually leaves only about three inches between them, but it can really increase the quantity you’re able to grow.

For sowing kohlrabi seeds, set them a quarter of an inch deep with just a light dusting of soil over top. Once they’ve germinated, thin them to your preferred spacing by cutting off excess sprouts with pruning shears. 

Set the seedlings at the same depth they were in their pot. For these vegetables, their bulb actually forms above ground, with only their cabbage-like roots underneath.

How to Grow

So now we’ve covered planting, and you might ask how to grow kohlrabi for the best results. Let’s talk about elements like garden soil and other important factors for good growth!

Light

Kohlrabi grows best in full sun… the more, the better. Make sure you choose a spot in your garden that receives at least six hours of full sunlight every day. The more sunlight the better the vegetable will form and grow.

Water

When considering how to grow kohlrabi, remember these vegetables need moisture to supply those bulbs, stems, and leaves. Keep the soil evenly moist at all times, applying more water when the first inch of soil dries out. A soaker hose is ideal for watering kohlrabi.

Kohlrabi grows best with an inch of water per week, but if the weather’s rainy, you can skip watering. As long as you keep the soil evenly moist, you’re good.

Soil

Kohlrabi needs fertile and well-drained soil to grow and produce healthy stems, leaves, and its bulbous base. Mulch the soil with plenty of organic matter, like composted manure for added nutrition and water absorption to keep the soil moist. Loose, well-worked soil is best for your kohlrabies to truly shine! The ideal soil pH level for growing kohlrabi ranges from 6.0 to 6.8. 

Temperature

The ideal temperature range for growing Kohlrabi is 40°F to 75°F (4-24°C).  Kohlrabi is heat-sensitive, and conditions that are too warm can make the kohlrabi bulb turn woody. It grows poorly in temperatures higher than 75°F (24°C) during the harvesting season. Kohlrabi can be grown in USDA growing zones 3 to 10. A spring for fall, and even late winter harvest, is possible.

Fertilizing

Fertilizing kohlrabi is a little tricky as they’re heavy feeders. Start with rich soil, to begin with, and side-dress every few weeks with well-rotted cow manure. Alternately, begin with rich soil but opt for regular fertilization using a nitrogen-rich fertilizer. A high nitrogen fertilizer should suffice, but follow the manufacturer’s instructions for the frequency of application.

When you’re growing kohlrabi in containers, regular fertilization is a must, as they will drain the soil of nutrients. They have shallow but large root systems, so apply your fertilizer in a ring around the plant, but don’t make contact with the bulbous stem base. The same is true of in-ground fertilization, but there’s less risk of water washing the fertilizer back against the vegetable in a normal bed setting.

Liquid fertilizers are also an option, but only if your soil retains the dissolved nutrients. If you have ample supplies of organic matter in the soil, regular applications of liquid fertilizer will work.

Maintenance

Pruning is not necessary when growing kohlrabi. The only time you’ll cut it is when you harvest. Otherwise, these vegetables are very low-maintenance, except they still require general care.

Propagation

Kohlrabi is typically propagated through seeds only. Other methods of propagation don’t result in good, healthy vegetables. Opt to grow kohlrabi from seeds from a reliable supplier.

Harvesting

The green leaves, long stems, and bulbous base of kohlrabi are all harvestable. Growing kohlrabi can be a lot of fun, and so is the time when you harvest kohlrabi for future meals! Whether you’re looking at a fall harvest or spring harvest, here’s how to do it. We’ll discuss how to store kohlrabi, too.

While we’ve covered how to grow kohlrabi, harvesting can be a bit tricky by comparison as it relies on what you plan to use. When you harvest kohlrabi, know that each portion has slightly different timing. Harvest kohlrabi leaves and stems from the outer portions of the base first, cutting off stems cleanly with pruning shears to reduce the risk of damage to the bulb. Leave the inner, uppermost stems and leaves intact until you’re ready to harvest the base as well.

Harvest kohlrabi leaves one by one at need. Stems should be at least the size of your finger or larger, although most harvest when the stems are about an inch in diameter. 

Once you grow kohlrabi to a size of two to four inches, you can harvest kohlrabi bulbs. More mature kohlrabi bulbs become woody with age. We recommend a good median size of about three inches. To harvest the base, remove the entire vegetable from the soil and cut off the root ends. Clip off leaves and stems flush with the bulb.

Storage

For best storage, place your kohlrabi harvest in a cold, moist location. Ideal conditions would include 95% relative humidity at 32 to 40°F (0-4°C). The closest approximation is to place your kohlrabi stems and base into a perforated plastic bag in the crisper drawer of your refrigerator.

The leaves can be left on the stems or removed, but the stems and base will last longer if the leaves are removed. Lay your leaves from a spring or fall, and even winter crop on a long piece of paper towel and then carefully wrap it into a tube. Put the tube of leaves into its own plastic bag. Use your leaves within a few days for best freshness.

Stems and bases can be frozen for long-term storage. Wash your kohlrabi and remove the stems from the base. Peel the tough outer layer of skin off. If desired, cut your kohlrabi into half-inch segments, although you can freeze it whole. Boil it in water (three minutes for whole stems/bases, one minute for diced pieces) and then immediately transfer it to cold water to stop cooking. Drain, pat dry, and lay the kohlrabi on a baking sheet to freeze until solid. Then, transfer it into a freezer storage bag. Store kohlrabi in the freezer for up to eight months.

Common Problems

While we’ve covered how to grow kohlrabi, there are a few issues you might encounter. Let’s go over how to handle problems that might arise while you’re growing kohlrabi in your garden.

Growing Problems

Woody bulbs can be caused by multiple issues: underwatering, age, or hot weather are the most common concerns. Make sure your vegetable has ample water, that it is not exposed to high temperatures for prolonged periods of time, and that you harvest it when it’s still tender.

Pests

Cabbage aphids congregate on the underside of leaves and along the stems. These annoying pests prefer a sheltered location whenever possible to protect themselves while they’re feeding. A hard spray of water knocks them off, and they won’t be able to get back on. For large outbreaks, neem oil or insecticidal soap is effective.

The beet armyworm is a larvae that can skeletonize leaves of your kohlrabi as well as other members of the cabbage family. To treat these before they devour your green leaves, apply a coating of Bacillus thuringiensis, which will gradually kill off the larvae.

Other caterpillars that might attack your kohlrabi include cabbage worms, cabbage loopers, and cutworms. All of these should also be treated with BT. Picking large caterpillars off the plant and dropping them into soapy water is a quick way to remove them. 

Flea beetles eat a shothole pattern into leaves and can become a nuisance. Neem oil is effective for the home gardener, but a dusting of diatomaceous earth over the leaves can also work to reduce their numbers.

Diseases

Alternaria leaf spot is a fungal disease that can cause brown or black spots on the foliage of infected plants. The lesions form rings and become brittle. It is caused by extended wet periods in colder months.

Black rot is a bacterial disease that is more common in seedlings than established vegetables and is easily confused with fusarium. V-shaped lesions may appear on the foliage, causing the leaves to turn brown and yellow until they collapse. Dark rings may also appear in the cross-section of the stem. Use healthy seeds, rotate the crop every two years, avoid sprinkler irrigation, and maintain good sanitation to avoid this problem.

Both downy mildew and powdery mildew are fairly common on the leaves of your kohlrabi. While these will not kill the kohlrabi in small amounts, large patches of diseased leaves can cause severe wilting and ruin the edible leaf surfaces. Applications of neem oil work as a preventative.

Frequently Asked Questions