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Growing Kohlrabi: How to Plant, Grow, and Harvest Kohlrabi | The Old Farmer's Almanac

How to Grow Kohlrabi: The Complete Guide

Photo Credit
Pixabay
Botanical Name
Brassica oleracea var. gongylodes
Plant Type
Sun Exposure
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Planting, Growing, and Harvesting Kohlrabi

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Kohlrabi is a cool-season vegetable, often overlooked because of its strange, almost alien appearance. But this edible’s fast growth and great taste make kohlrabi something every gardener should try. Here’s how to plant, grow, and harvest kohlrabi!

About Kohlrabi

Kohlrabi can be grown as a spring or fall crop; hot summer temperatures will stress the plant and hamper the growth of its nutritious, bulb-shaped stem.

Kohlrabi, which can be either purple or green, is a member of the Brassica family (alongside broccoli, cabbagebrussels sprouts, and many others). It’s a biennial; in the first year, the bulb-shaped stem grows. In the second year, the plant will flower and produce seeds. 

When eating, the outer tough layer needs to be removed with a vegetable peeler. The interior white flesh is sweet and tender with a crisp texture and peppery flavor. In terms of taste, think of kohlrabi as a milder turnip. Some folks say it tastes somewhat of apple. It can be eaten raw, sprinkled with salt and lime or lemon juice. Or, slice thin and add to salads. You can cook kohlrabi but only lightly, added last in a stir-fry.

Kohlrabi is not only enjoyed for its taste but its nutritional value. It offers vitamins C, A and K; minerals like calcium, potassium and iron; and phytochemicals that protect against certain cancers. Kohlrabi greens are also nutritious, containing carotenes, vitamins and minerals. Like other Brassicas, both the stem and greens are rich in dietary fiber that aids digestive health.

If given a chance, kohlrabi is simple to grow, fast to mature (in as little as 6 weeks), and is generally pest-free. Give it a try!

Image credit: Vaitekune/GettyImages


 

Planting

Plant in a location that receives ample sunlight (at least 6 hours, more is better) and has rich, slightly acidic, well-draining soil. While kohlrabi isn’t a heavy feeder, it is helped by having its soil dressed with 1 inch of compost before planting.

Avoid planting kohlrabi where other vegetables in the Brassica family have been grown in the previous 2 or 3 years. This helps to prevent the spread of disease and nutrient deficiencies.

When to Plant Kohlrabi

See our spring and fall planting dates for kohlrabi for your zip code or postal code.

  • In spring, once soil temperatures have reached at least 45°F (7°C), sow seeds directly in the garden, for an early to mid-summer harvest.
  • To start indoors, sow seeds 6 to 8 weeks prior to your last spring frost dateHarden off seedlings before planting outdoors, too.
  • For a fall harvest, sow seeds outdoors in mid- to late summer. 
  • In warmer regions such as the southern U.S., it may be grown as a winter crop, too.

How to Plant Kohlrabi

  • Sow seeds 1/4 to 1/2 inch deep.
  • In rows, space kohlrabi seeds about 2 inches apart in rows 10 to 12 inches apart.
  • Once seedlings have emerged (4 to 7 days), thin them to every 5 to 8 inches.
  • Stagger sowing every 2 to 3 weeks for a continuous summer.  

Watch a video on planting and growing kohlrabi: 

Growing
  • If humidity is low, help to keep the soil moist by spreading a thin layer of straw or bark mulch around the base of the plant.
  • Water 1 inch per square foot per week, unless the soil seems to be drying out sooner.
  • Be diligent about weeding around kohlrabi, but be careful not to disturb its roots while the plant is still young.

Purple kohlrabi

Harvesting
  • To harvest, cut the kohlrabi root off at ground level with a sharp knife when the bulbous stems are between 2 and 4 inches in diameter. 
  • The stem should be succulent, tender, and sweet at this size. If allowed to become too large, it can become tough and bitter.

How to Store Kohlrabi

  • Harvested stems can be stored with other root crops in a cool, humid place or in the refrigerator for up to 4 weeks. Remove the leaf stems and wash the stem thoroughly before storing.
Gardening Products
Wit and Wisdom
  • Kohlrabi gets its name from German Kohl (“cabbage”) and Rübe (“turnip”). Quite a fitting name for this oddball veggie!
  • Kohlrabi is a relatively new vegetable, having first been documented about 500 years ago. In the United States, it has been grown since at least as far back as 1806.
Pests/Diseases
Kohlrabi Pests and Diseases
Pest/DiseaseTypeSymptomsControl/Prevention
AphidsInsectMisshapen/yellow leaves; sticky “honeydew” (excrement); sooty, black moldGrow companion plants; knock off with water spray; apply insecticidal soap; put banana or orange peels around plants; wipe leaves with a 1 to 2 percent solution of dish soap (no additives) and water every 2 to 3 days for 2 weeks; add native plants to invite beneficial insects
Black rotFungusYellow, V-shape areas on leaf edges that brown and progress toward leaf center; leaves eventually collapse; stem cross sections reveal blackened veinsDestroy infected plants; choose resistant varieties; provide good drainage; remove plant debris; rotate crops
Cabbage loopersInsectLarge, ragged holes in leaves from larval feeding; defoliation; stunted or bored heads; excrementHandpick; add native plants to invite beneficial insects; spray larvae with insecticidal soap or Bt; use row covers; remove plant debris
Cabbage root maggotsInsectWilted/stunted plants; off-color leaves; larvae feeding on rootsUse collars around seedling stems; monitor adults with yellow sticky traps; use row covers; destroy crop residue; till soil in fall; rotate crops
CabbagewormsInsectLeaves have large, ragged holes or are skeletonized; heads bored; dark green excrement; yellowish eggs laid singly on leaf undersidesHandpick; use row covers; add native plants to invite beneficial insects; grow companion plants (especially thyme); spray Bacillus thuringiensis (Bt)
ClubrootDiseaseWilted/stunted plants; yellow leaves; roots appear swollen/distortedDestroy infected plants; solarize soil; maintain soil pH of around 7.2; disinfect tools; rotate crops
CutwormsInsectWilting; severed stems of seedlings and transplants just above or below soil line; whole seedlings disappearHandpick; in spring before planting, cultivate soil to reduce larvae; wrap a 4-inch-wide collar made from cardboard or newspaper around each stem, sinking 2 inches into soil; weed; use row covers; destroy crop residue
Downy mildewFungusYellow, angular spots on upper leaf surfaces that turn brown; white/purple/gray cottony growth on leaf undersides only; distorted leaves; defoliationRemove plant debris; choose resistant varieties; ensure good air circulation; avoid overhead watering
Flea beetlesInsectNumerous tiny holes in leavesUse row covers; mulch heavily; add native plants to invite beneficial insects
Powdery mildewInsectWhite spots on upper leaf surfaces expand to flour-like coating over entire leaves; foliage may yellow/die; distortion/stunting of leavesDestroy infected leaves on plants; choose resistant varieties; plant in full sun, if possible; ensure good air circulation; spray plants with 1 teaspoon baking soda dissolved in 1 quart water; destroy crop residue
ThripsInsectLeaves, especially in folds near base, have white patches or silver streaks; brown leaf tips; blistering/bronzing on leaves; bulbs/ heads distorted or stunted; curling or scarringRemove plant debris; choose resistant varieties; add native plants to invite beneficial insects; use row covers; use straw mulch; monitor adults with yellow or white sticky traps; use sprinklers or other overhead watering
Aphids on kohlrabi leaf. Photo by GrowVeg.
Aphids are a common pest of kohlrabi and other members of the cabbage family (Brassicas). Photo by GrowVeg.
Cooking Notes

Here’s a simple raw kohlrabi recipe. Peel the bulb (if larger than 3 inches in diameter) and cut into large disks. Put in a bowl. Add salt to taste, juice of 1/2 lime, and chilly pepper. Enjoy!

Or, try adding kohlrabi to a slaw, grating cabbage and carrots and kohlrabi in tender shreds. Add shredded apple or pear and perhaps a radicchio. It’s a nice alternative to plain coleslaw. Toss with salt and sugar to soften them slightly and draw out moisture. Serve with a Dijon-based vinaigrette. 

About The Author

Catherine Boeckmann

Catherine Boeckmann loves nature, stargazing, and gardening so it’s not surprising that she and The Old Farmer’s Almanac found each other. She leads digital content for the Almanac website, and is also a certified master gardener in the state of Indiana. Read More from Catherine Boeckmann

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