How to Grow Kohlrabi

Growing guide

Overview

Kohlrabi is a cool-season brassica grown for its swollen, crisp stem that tastes like a mild, sweet broccoli stem. It’s one of the fastest vegetables you can grow, ready in 45–60 days, and it tolerates light frost. Give it full sun, steady moisture, and well-drained soil, and it will reward you with tender bulbs from spring through fall.

Soil & planting prep

Kohlrabi grows best in loamy or clay soil that drains well and holds moisture. Aim for a pH between 6.0 and 7.0. Work in 2–3 inches of compost before planting, and space plants 6–8 inches apart in rows 12–18 inches apart. Sow seeds ¼ to ½ inch deep.

When to plant

Start seeds indoors 4 weeks before your last frost date, or direct sow as soon as the soil can be worked in spring. For a fall crop, sow seeds 8–10 weeks before your first fall frost. Kohlrabi is frost-tolerant, so light frosts won’t kill it, but prolonged heat makes the bulbs woody.

How to plant

1. Choose a spot in full sun with well-drained soil. Mix in compost to a depth of 6–8 inches.
2. Sow seeds ¼ to ½ inch deep, either indoors in cells 4 weeks before last frost or directly in the garden after the soil reaches 45°F.
3. When seedlings have 2–3 true leaves, thin them to 6–8 inches apart. If transplanting, set them at the same depth they grew in the pot.
4. Water gently after planting and keep the soil evenly moist—about 1 inch of water per week, more in hot weather.
5. Mulch with straw or grass clippings to retain moisture and suppress weeds. Avoid disturbing the roots when weeding.

5 common mistakes to avoid

• Letting the bulbs grow too large—kohlrabi becomes woody and tough once it exceeds 2–3 inches in diameter. Harvest on time, when bulbs are 2–3 inches across.
• Planting in midsummer heat—kohlrabi is a cool-season crop and hot weather makes bulbs fibrous and bitter. Plant in early spring or late summer for a fall crop.
• Inconsistent watering—dry spells followed by heavy watering cause the bulbs to split. Keep the soil consistently moist with about 1 inch of water per week.
• Overcrowding—if you don’t thin seedlings to 6–8 inches apart, plants compete for nutrients and water, resulting in small, poorly formed bulbs. Thin ruthlessly when plants are 2–3 inches tall.
• Skipping frost protection for fall crops—although kohlrabi tolerates light frost, a hard freeze can damage the bulbs. Use row cover or harvest before temperatures drop below 25°F.

Harvesting & storage

Harvest kohlrabi when the bulb is 2–3 inches in diameter—about 45–60 days after planting. Cut the stem at soil level with a sharp knife, then trim off the leaves and roots. Store bulbs in the refrigerator crisper for up to 2–3 weeks; they also freeze well after blanching.

Companion planting

Kohlrabi grows well with beets, onions, and aromatic herbs like dill and mint. Avoid planting near tomatoes or pole beans, which can stunt its growth.

Growing in containers

Kohlrabi is container-friendly. Use a 5-gallon pot per plant with drainage holes and a quality potting mix. Keep it in full sun and water regularly, as containers dry out faster than garden soil.

Pro tips

Start indoors 4-6 weeks before last frost or direct sow. Thin to 6-8 inches. Harvest when bulbs are 2-3 inches diameter — bigger gets woody. Great for fall crops too.