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Planting, Growing, and Harvesting Kohlrabi
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, cabbage, brussels 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!
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.
Pests/Diseases
| Pest/Disease | Type | Symptoms | Control/Prevention |
|---|---|---|---|
| Aphids | Insect | Misshapen/yellow leaves; sticky “honeydew” (excrement); sooty, black mold | Grow 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 rot | Fungus | Yellow, V-shape areas on leaf edges that brown and progress toward leaf center; leaves eventually collapse; stem cross sections reveal blackened veins | Destroy infected plants; choose resistant varieties; provide good drainage; remove plant debris; rotate crops |
| Cabbage loopers | Insect | Large, ragged holes in leaves from larval feeding; defoliation; stunted or bored heads; excrement | Handpick; add native plants to invite beneficial insects; spray larvae with insecticidal soap or Bt; use row covers; remove plant debris |
| Cabbage root maggots | Insect | Wilted/stunted plants; off-color leaves; larvae feeding on roots | Use collars around seedling stems; monitor adults with yellow sticky traps; use row covers; destroy crop residue; till soil in fall; rotate crops |
| Cabbageworms | Insect | Leaves have large, ragged holes or are skeletonized; heads bored; dark green excrement; yellowish eggs laid singly on leaf undersides | Handpick; use row covers; add native plants to invite beneficial insects; grow companion plants (especially thyme); spray Bacillus thuringiensis (Bt) |
| Clubroot | Disease | Wilted/stunted plants; yellow leaves; roots appear swollen/distorted | Destroy infected plants; solarize soil; maintain soil pH of around 7.2; disinfect tools; rotate crops |
| Cutworms | Insect | Wilting; severed stems of seedlings and transplants just above or below soil line; whole seedlings disappear | Handpick; 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 mildew | Fungus | Yellow, angular spots on upper leaf surfaces that turn brown; white/purple/gray cottony growth on leaf undersides only; distorted leaves; defoliation | Remove plant debris; choose resistant varieties; ensure good air circulation; avoid overhead watering |
| Flea beetles | Insect | Numerous tiny holes in leaves | Use row covers; mulch heavily; add native plants to invite beneficial insects |
| Powdery mildew | Insect | White spots on upper leaf surfaces expand to flour-like coating over entire leaves; foliage may yellow/die; distortion/stunting of leaves | Destroy 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 |
| Thrips | Insect | Leaves, 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 scarring | Remove 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 |
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.
Catherine Boeckmann
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