How to Grow Kohlrabi

kohlrabi

Story at-a-glance -

  • Kohlrabi is pale green or purple, resembling a turnip bulb with large stems and leaves; related to cabbage and broccoli, the plant grows easily at home, providing you with a pesticide-free and tasty addition to salads and soups or as a side dish
  • Kohlrabi is a cool weather plant and appreciates full sun with temperatures between 40 F and 75 F; they grow quickly in well-drained soil with good moisture retention
  • Harvest your plants when the bulbs are 2 to 4 inches in diameter, as any further growth often results in a more fibrous and woody texture
  • Kohlrabi is nutrient-dense and high in fiber, adding significant health benefits to your nutrition plan; it may be boiled, mashed, roasted or sliced and eaten raw or added to salads

By Dr. Mercola

Kohlrabi (Brassica oleracea) looks like a pale green or purple turnip with multiple stalks of green leaves. Although the plant looks like a turnip, it's actually related to cabbage and broccoli.1 The bulb grows above ground and is not a root vegetable.

Also known as a "space cabbage" from its appearance, this down-to-earth vegetable offers some of the same health benefits as others in the family, including broccoli, cauliflower, kale and mustard.

But, unlike its relatives, the plant is easier to grow, matures quickly and is ideal for fall or early spring planting. With a swollen, bulb-like stem sprouting waxy leaf stalks, the plant has an out-of-the-world appearance and may take the crown for the most unusual looking vegetable.2

Kohlrabi thrives in your garden or in containers. Most find it easy to grow and less prone to pests and disease than some of the relatives. You'll want to consider planting it in your garden this fall or next spring to enjoy some of the pleasing flavor and health benefits.

History of the Cabbage Turnip

The name kohlrabi comes from the German word "kohl" meaning cabbage and "rabi" meaning turnip, an apt description of the plant. The origins of kohlrabi are unclear, but the plant was first mentioned by Roman author and naturalist Pliny the Elder, in the first century.3

The vegetable was well-known to the Roman Empire and likely grew in many parts. By 800 A.D., Emperor Charlemagne ordered kohlrabi to be grown in his Imperial Gardens. By the 1600s it had spread to India where it became a staple crop. It wasn't until the late 20th century that it was grown in many other parts of the world and recipes were developed for cooking the root and the leaves.

Kohlrabi was first grown in the U.S. in 1806, but while available in America, it is not commonly found outside of the southern states. What the plant lacks in appearance it makes up for in flavor. It is described as having a "sweet flavor that is somewhere between a turnip and a water chestnut, with a crisp, crunchy texture."4

The plant is versatile and offers health benefits and nutrition from both bulb and leaves. It can be cooked, eaten raw in salads, grilled, roasted or added to vegetable pies. The leaves are often enjoyed as you would spinach, beet greens or collard greens, and taste like kale and collards.

Growing Conditions in Your Garden or Pots

Kohlrabi grows well in your garden or containers. The plants appreciate full sun but will adapt to dappled shade.5 They grow best in cooler temperatures, between 40 and 75 degrees Fahrenheit (F). In warmer climates, consider planting in late fall for a winter harvest.

Allow 45 to 60 days for plants sown from seed to reach maturity. Stephen Reiners, professor of horticulture and chair of Cornell's School of Integrative Plant Science, advises:6

"You can grow kohlrabi in almost any region if you grow it in the spring or fall. Good timing is key. You want to avoid having the bulbs form in hot weather, which can make them woody."

Use well-draining soil in a raised bed, container or garden, steering clear of clay. The plants are not heavy feeders, so working a generous layer of compost — about 1 inch — into the soil before planting, with a little extra added on the side of the plant as the bulb begins to swell, is often enough.7

The plant does best in alkaline soil, at least a pH of 6.0 or higher. If your garden soil tests more acidic, it is wise to add lime to the area several weeks before planting. If you're growing in containers, composted soil is appreciated. Plant seeds one-fourth to one-half inch deep and once sprouted, thin the seedlings 2 to 5 inches apart.8

Water after sowing to thoroughly wet the ground. Although they cope with heat, when you allow the soil to dry, the plant becomes tough and woody. Stress affects the growth of the bulb, so even temperatures and consistent soil moisture is key. The best way is to ensure these soil conditions is to provide plenty of organic matter, such as compost or grass clippings from an untreated lawn.9

Adding a layer of organic mulch helps moderate soil temperature, moisture and nutrients as well. However, when planting an early spring crop, take care to only add mulch after the soil has warmed or you risk stunting plant growth by keeping the soil cool.

Harvest Time Controls the Size of Your Plant

This short video demonstrates how to harvest the plant once it reaches maturity. The plant is fast growing, and tastes best when 2 to 4 inches in diameter.10 Once planted, you'll see stems begin to swell and form globes within weeks. When you harvest depends on your climate and whether it's a spring or fall crop.

In the spring months, the bulb is most tender and mild flavored when it is no more than 3 inches in diameter. Fall crops may stay tender slightly longer and the plant can tolerate temperatures to a light frost, giving you more time to harvest and eat.11

Once the bulb gets to the size of a tennis ball, it becomes more fibrous and woody, losing much of the tender cabbage flavor. However, the leaves continue to be flavorful and useful when steamed or added to salads.12

If you've planted a large crop in the fall and can't eat them immediately, consider trimming the leaves, wrapping the bulbs in plastic and storing in your refrigerator or a cool, dry area like a root cellar. The bulbs will stay fresh for several months.13

When planting a fall crop you may thin the seedlings closer together, leaving 7 to 8 inches between the rows.14 A late crop may be planted at least four weeks prior to expecting the first frost. The cooler weather slows the growth near harvest, giving you more time to pick fresh from the garden.

Pests and Disease — Prevention and Treatment

Kohlrabi doesn't have many difficult pest or disease problems. One of the more common is the cabbage aphid,15 a gray green insect that forms a dense colony on the plant. Aphids damage the plants by contaminating the harvest, excreting honeydew, which causes the leaves to turn black.

If the infestation is limited to a few leaves or shoots, they may be pruned to provide control. Sturdy plants can be sprayed with a strong jet of water to knock the insects from the plant.

The cabbage looper 16 insect overwinters in crop debris in the soil. They leave large or small holes in the leaves and often cause extensive damage. The caterpillars are pale green with white lines running down both sides of the body. They are usually held in check by their natural enemies, but if they become a problem, the larvae can be hand-picked from the plants.

Fungal diseases may occur after a heavy rainfall and warm temperatures or when the soil does not drain well. Provide adequate air circulation between the leaves and plants, rotate crops in your garden, keep them free of plant debris and look for fungal resistant plant varieties.17

Nutrition and Health Benefits

Kohlrabi has been popular among Europeans for centuries, but is often bypassed in North America, where broccoli and cauliflower are preferred. However, this tender cousin is quickly becoming popular, as it is a good source of fiber, low in calories and high in flavor.

The plant also provides sulfur-containing glucosinolates, also found in broccoli, Brussels sprouts, cauliflower and cabbage.18 These compounds enhance your body's antioxidant function and may also help to reduce your risk of cancer. Kantha Shelke, a food scientist at the food and science research firm, Corvus Blue LLC, and spokesperson for the Institute of Food Technologists, told Time:19

"Kohlrabi's chemopreventive effects makes it particularly healthy. Kohlrabi contains isothiocyanates which are effective against cancer.

The chemopreventive compounds are more bioavailable from fresh — about three times as much as from cooked — kohlrabi; the higher bioavailability is associated with a higher chemopreventive activity, which might be the reason why raw kohlrabi is preferentially consumed by health-conscious people."

Just as kohlrabi offers a variety of culinary uses, there are a wide array of benefits to your body as well. With only 36 calories for every 135-gram serving, the vegetable delivers vitamin A, calcium, vitamin C, iron and 4 grams of fiber.20 

Interestingly, the plant is exceptionally high in vitamin C, vital for maintaining healthy connective tissues, teeth and gums as well as supporting your immune health.21 The phytochemical antioxidants may help lower your risk of diabetes, heart disease, stroke and Alzheimer's disease.

The plant also contains copper, manganese, iron and potassium, and is rich in phytochemicals and carotenes. Some of the ways kohlrabi may benefit your health include:22

Promotes healthy digestion

Helps with weight management

Keeps nerves and muscle functioning optimally

Maintains healthy blood pressure levels

Maintains healthy metabolism

Boosts bone strength

Promotes vision health

Consider Adding These Recipes to Your Menu

Kohlrabi is one of the most versatile vegetables you can add to your menu. The bulb may be eaten raw, mashed, sautéed, grilled or roasted. It may be added to salads, soups, stews or eaten as a side dish. Different cultures around the world also have different ways of cooking kohlrabi, making use of this crop in a variety of creative ways.

Shelke says in countries near the equator, kohlrabi is often grated and transformed into kohlrabi fritters, pancakes or flat breads. In India, pickled kohlrabi mixed with turmeric powder, salt, dry mustard powder, oil and vinegar is a well-loved treat, and is served with yogurt and bread. This is also how kohlrabi is enjoyed in Tibet, Nepal and northern China.23 If you want to try kohlrabi, here are two recipes, one cold and one roasted:

Carrot and Kohlrabi Slaw (Recipe adapted from The Kitchn)24

Ingredients

  • 1 large kohlrabi, peeled, stems trimmed off, grated
  • 1/4 head purple cabbage, shredded
  • 2 medium carrots, peeled and grated
  • 1/2 red onion, grated
  • 4 tablespoons chopped cilantro
  • 1/4 cup golden raisins (optional)
  • 1/4 cup mayonnaise
  • 1 tablespoon cider vinegar
  • 1 tablespoon raw honey
  • 1 teaspoon salt

Procedure

  1. In a large bowl, mix the kohlrabi, carrots, cabbage, onion, cilantro and raisins (if using).
  2. In a smaller bowl, whisk together the cider vinegar, mayonnaise, salt and honey.
  3. Pour the dressing over the slaw, and mix until all the ingredients are fully coated. Chill for several hours before serving.

Roasted Kohlrabi (Recipe adapted from All Recipes)25

Ingredients

  • 4 kohlrabi bulbs, peeled
  • 1 tablespoon olive oil
  • 1 clove garlic, minced
  • Salt and pepper to taste
  • 1/3 cup Parmesan cheese, grated

Procedure

  1. Heat your oven to 450 degrees F.
  2. Cut the kohlrabi bulbs into 1/4-inch slices and then cut the slices in half.
  3. Combine the olive oil, garlic, salt and pepper in a large bowl. Toss the slices in the olive oil mixture to coat the slices.
  4. Spread the kohlrabi in a single layer on a baking sheet, baking in the preheated oven and stirring occasionally so the vegetables brown evenly, approximately 15 to 20 minutes.
  5. Remove and sprinkle with grated Parmesan cheese. Return to the oven to allow the cheese to brown and serve immediately.