Kohlrabi: Direct Sow Vegetable
How to Sow
Sowing Directly in the Garden:
- Sow seeds after danger of frost in spring. In frost free areas, sow in fall.
- Sow in well-worked soil in full sun. Do not plant cabbage family crops in the same place 2 years in a row.
- Prepare the bed by turning the soil under to a depth of 8 inches. Level with a rake to remove clumps of grass and stones.
- Sow seed thinly in rows 18 inches apart and cover with ¼ inch of fine soil.
- Firm lightly and keep evenly moist.
- Seeds emerge in 14-21 days.
- This to stand about 4 inches apart when seedlings are 1-2 inches tall.
How to Grow
- Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating. Avoid disturbing the soil around the plants when weeding.
- Keep plants well watered during dry periods to promote rapid, uninterrupted growth. Plants need about 1 inch of rain per week during the growing season. Use a rain gauge to check to see if you need to add water. It’s best to water with a drip or trickle system that delivers water at low pressure at the soil level. If you water with overhead sprinklers, water early in the day so the foliage has time to dry off before evening, to minimize disease problems. Keep the soil moist but not saturated.
- Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.
Harvest and Preserving Tips
- Harvest the foliage when bulbs reach 2-3 inches in diameter and foliage is still young and tender.
- Eat the stems fresh or use them as spinach substitute.
- Use the bulb fresh or cooked. If using fresh, peel the root prior to using. If baking, it can be peeled or left unsliced, depending on the recipe.
- Store kohlrabi with leaves removed. Can be stored in the refrigerator for several weeks. Storage life can be extended if kohlrabi is placed in a sealed plastic bag.
- Kohlrabi may be blanched, peeled and sliced, and frozen.
- Kohlrabi may also be pickled.
Common Disease Problems
Alternaria Leaf Spot: Small, round reddish brown spots with white to gray centers form on the upper surface of the leaves and along the midrib. The lesions may encircle the stems and cause wilt. This disease is worse in warm, wet or very humid weather. Burpee Recommends: Avoid getting water on the foliage. Remove infected plant parts and do not work around wet plants. Provide plenty of air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Clubroot: Leaf symptoms include stunting, yellowing and wilt. When the plants are removed from the roots may have galls, swelling and distortion of the roots. Burpee Recommends: Test the soil pH Clubroot is most common in acid soil and lime to raise pH. Avoid planting where Brassica plants were grown the previous year.
Damping Off: This is one of the most common problems when starting plants from seed. The seedling emerges and appears healthy; then it suddenly wilts and dies for no obvious reason. Damping off is caused by a fungus that is active when there is abundant moisture and soils and air temperatures are above 68 degrees F. Typically, this indicates that the soil is too wet or contains high amounts of nitrogen fertilizer. Burpee Recommends: Keep seedlings moist but do not overwater; avoid over-fertilizing your seedlings; thin out seedlings to avoid overcrowding; make sure the plants are getting good air circulation; if you plant in containers, thoroughly wash them in soapy water and rinse in a ten per cent bleach solution after use.
Downy Mildew: This fungus causes whitish grey patches on the undersides and eventually both sides of the leaves. Burpee Recommends: Rotate crops with plants in a different family. Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations
Common Pest and Cultural Problems
Cabbage Looper: These worms are green with a white stripe on either side, about 1-1.5 inches long. They tunnel through the bulbs. Burpee Recommends: Hand pick. Floating row covers can help prevent their laying eggs on the plants.
Cutworms: These insects cut off the seedlings at the soil level. Burpee Recommends: Place a paper cup collar (use a coffee cut with the bottom cut out) around the base of the plant. They are usually mostly a problem with young seedlings. You can also control by handpicking and controlling weeds, where they lay their eggs.
Flea Beetles: These small hopping beetles feed on plant foliage and may spread diseases. Burpee Recommends: Rotate crops with plants in a different plant family. Use floating row covers to prevent damage to young foliage.
Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage.
Thrips: Thrips are tiny needle-thin insects that are black or straw colored. They suck the juices of plants and attack flower petals, leaves and stems. The plant will have a stippling, discolored flecking or silvering of the leaf surface. Thrips can spread many diseases from plant to plant. Burpee Recommends: Many thrips may be repelled by sheets of aluminum foil spread between rows of plants. Remove weeds from the bed and remove debris from the bed after frost. Check with your Cooperative Extension Service for pest controls.
What parts of kohlrabi are edible? The bulb, stem and leaves are all edible.
Should kohlrabi be eaten fresh or cooked? Kohlrabi may be eaten raw in salads or cooked, like a turnip.
Can kohlrabi be grown in containers? Yes it can! Be sure to use a commercial potting mix rather than garden soil.
Why did my kohlrabi bulb become woody? Kohlrabi is a cool season crop. When the bulb is harvested too late it can become tough and woody. This can also happen when the weather turns hot in early summer.
Why did my kohlrabi not form a bulb? This can happen when plants are spaced too closely together. It can also come from poor growing conditions such as too warm or freezing temperatures, too little water or a nutrient deficiency.