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How to Grow Kohlrabi

Grow kohlrabi for the enlarged stems--white, purple, or green.

Grow kohlrabiKohlrabi is a hardy biennial grown as an annual. Kohlrabi is grown for its swollen base which is actually the plant’s stem. The globe-shaped base develops above the ground. Kohlrabi is a good choice for gardens that don’t have deep soils.

Varieties with white, light green or purple skins are available. Both the globe base and leaves can be eaten.

Sow kohlrabi seed in the garden 3 to 4 weeks before the last average frost date in spring. Kohlrabi grows best in cool temperatures between 40°F and 75°F (4.4°C and 23.9°C). Kohlrabi requires 45 to 60 days to reach maturity. In warm winter regions, sow kohlrabi in late summer for winter harvest. Kohlrabi can withstand an early autumn frost.

Description. Kohlrabi is a hardy biennial grown as an annual. Kohlrabi has a swollen globe-shaped stem that makes it look like a turnip growing on a cabbage root. Stems can be white, purple, or green and are topped with a rosette of long-stemmed blue-green leaves. Kohlrabi is milder and sweeter than either cabbage or turnip.

Yield. Plant 4 to 5 kohlrabi per household member.

Kohlrabi seedlings
Kohlrabi seedlings

Planting Kohlrabi

Site. Plant kohlrabi in full sun. Grow kohlrabi well-worked, well-drained soil rich in organic matter. Work 2 inches (5cm) of aged compost into the soil before you begin planting. Kohlrabi prefers soil within the 5.5 to 6.8 range. Side dress kohlrabi with aged compost at midseason.

Indoor starting. Kohlrabi seeds can be started indoors or in a cold frame or plastic tunnel.

Spring planting time. Kohlrabi is a cool-weather crop. Sow kohlrabi seed in the garden 3 to 4 weeks before the last average frost date in spring. Kohlrabi requires 45 to 60 days to reach maturity and should be grown so that it comes to harvest before temperatures average greater than 75°F (23.9°C). Grow kohlrabi for fall harvest in hot-summer regions.

Planting for fall or winter harvest. In warm winter regions, you can grow kohlrabi through the winter. Sow kohlrabi in late summer for winter harvest. Kohlrabi can withstand an early autumn frost. In cold winter regions, sow kohlrabi in summer for early autumn harvest.

Succession crops. You can sow kohlrabi seeds as long as temperatures are greater than 40°F  (4.5°C).

Cold-weather care. If you are growing kohlrabi for late fall or winter harvest, protect plants with row covers or a plastic tunnel if nighttime temperatures below 25°F (-4°C) are predicted.

More tips at Kohlrabi Seed Starting Tips.

Planting and spacing. Sow kohlrabi seed ½ inch deep and 1 inch (2.5 cm) apart; thin successful seedlings from 5 to 8 inches (12-20cm) apart. Space rows 18 to 24 inches (45-60 cm) apart. Thinned seedlings can be transplanted to another part of the garden.

Intensive spacing. Sow seed or set out transplants 4 to 6 inches (10-15cm) apart in a staggered double row.

How much to grow. Grow 6 to 10 plants per person.

Companion plants. Beets, celery, herbs, onions, potatoes. Do not plant with pole beans, strawberries or tomatoes.

Container. Kohlrabi is large rooted and not well suited for container growing.

Kohlrabi in garden
Keep the soil evenly moist as kohlrabi grows to harvest.

Caring for Kohlrabi

Water and feeding. Keep soil evenly moist for quick growth. Kohlrabi that goes without water will become woody. Prepare planting beds with aged compost. Side dress kohlrabi with aged compost once a month. Alternatively, you can fee kohlrabi once a month with a plant-starter fertilizer or a balanced organic fertilizer.

Care. Cultivate carefully to avoid harming the shallow roots. Mulch kohlrabi with aged compost when plants are 4 to 5 inches (10-12 cm) tall.

Pests. Kohlrabi can be attacked by cutworms, cabbage loopers, and imported cabbage worms. Place collars around stems to protect seedlings from cutworm damage. Remove egg clusters from underneath leaves and wash plants with diluted soap solution. Cabbage worms can be controlled by spraying with Bacillus thuringiensis.

Diseases. Kohlrabi is susceptible to cabbage yellows, clubroot, and downy mildew. Plant disease-resistant varieties. Remove and destroy infected plants.

Purple kohlrabi
‘Early Purple Vienna’ kohlrabi

Harvesting and Storing Kohlrabi

Harvest. Kohlrabi is ready for harvest when stem globes reach 2 to 3 inches (5-7cm) in diameter. Globes that grow larger than 3 inches (7.5cm) in diameter may become woody. Kohlrabi leaves can be harvested for the table; cook them like you would other greens.

If the skin of a globe is tough, peel away the outer layer; the center may still be tender and flavorful.

Winter harvest. In mild-winter regions, leave kohlrabi in the ground over the winter and harvest globes as needed.

More tips at How to Harvest and Store Kohlrabi.

Storing and preserving. Kohlrabi will store well in the refrigerator for 1 to 2 weeks or for one to two months in a cold, moist place. Kohlrabi can be peeled and diced for freezing.

Kohlrabi Varieties to Grow

Varieties. ‘Early Purple Vienna’ (60 days); ‘Early White Vienna’ (55 days); ‘Grand Duke’ (50 days); ‘Purple Danube’ (52 days); ‘Kolibri’ (50 days).

‘Early White Vienna’ produces compact plants; light green skin and white flesh globes; this variety is slow to bolt; grow from seed in 50 to 55 days.

‘Grand Duke’ produces green-skinned globes to 4 inches (10cm) in diameter; grow from seed in 48 to 50 days.

‘Kolibri’ produces purple globes with white flesh; it can tolerate heat; grow from seed in 50 days.

Common name. Kohlrabi, turnip-rooted cabbage, stem turnip, turnip cabbage, German turnip

Botanical name. Brassica oleracea, Gongylodes group

Origin. Hybrid

Grow 80 vegetables: KITCHEN GARDEN GROWERS’ GUIDE

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33 Comments

  1. I am having a problem with radicchio. My gardening friend and I planted it years ago in spring; it never came to a head. My friend read somewhere that it was a two year plant. We planted seedlings late last spring and now I have a healthy plant, cupping leaves but no sign of a head. (I don’t know the variety we planted.) So, what am I doing wrong?

  2. Persuading radicchio to form a head can be difficult, but not impossible. Only 10 to 50 percent of heading varieties actually form a head without special attention; so you can see success can be difficult Here are a few suggestions to get the results you want:
    1. Choose a variety that more easily heads, here are several in order or best success: Indigo, Fiero, Chiogga Red, Prima Rosa, Carmen.
    2. Plant for fall harvest: sow seeds in the garden 85 days before the first frost in fall; radicchio requires a long, cool season. Spring planted crops have less success.
    3. Place a plastic mulch or plastic sheeting around the radicchio plants–white, black, or clear. Growing radicchio on plastic, not the soil, will increase the heading percentage significantly.
    Finally, radicchio leaves can be eaten even if a head does not form; so once leaves are 4 to 5 inches long harvest them from the outside in cut-and-come-again fashion and enjoy the flavor of young, tender leaves.

  3. I planted kolrabi between peppers and tomatoes. Two questions: Why are they so small, just ping-pong ball size? Why arent you supposed to plant kohlrabi by tomatoes?

  4. Small Kohlrabi: Kohlrabi likes cool weather. It is fast growing and matures quickly, so it is a good choice spring and fall planting. Direct-seed kohlrabi about the time of the last spring frost date and for a fall crop about 8 to 10 weeks before the first fall frost date. If you live in a region where summer weather does not get too warm, you can make successive sowings of kohlrabit every 2 weeks. Kohlrabi is best harvested young and small, when the bulbs are about 2 inches in diameter–this size kohlrabi will be sweet, crisp, and tender. If bulbs get too much bigger they will turn woody and fibrous. Kohlrabi is a member of the cabbage family–to allow for the simple management of pests and diseases–and because the growing requirements are different, it’s best, but not essential, that you plant kohlrabi away from tomato family vegetables.

  5. What could be the cause of the bulb not forming? The stem just continues to grow into an elongated tube, not the usual round bulb. Thanks

    • Poor bulb formation in kohlrabi can be the result of uneven watering or soil lacking in nutrients, or both. Water kohlrabi whenever the top inch or two turns dry–you may need to water a couple of times a week. Apply organic mulch to maintain even soil moisture. Water kohlrabi with compost tea which will be rich in nutrients; this is very important if the soil is only average. Even, steady growth comes with even, steady watering and feeding.

    • You may have waited a bit too long for this crop of kohlrabi. It’s best to mark your calendar on the day you plant kohlrabi–count ahead the expected days to maturity and then be ready to harvest on or around that date. The flavor and quality of the stems declines as soon as the plant starts to flower.

  6. How to grow seeds of kholrabi .I plant the seedlings and left it for all summer for seed because the plant grown well but instead of flower the plant grow very large and due to no flowers I uproot the plant at early monsoon and plant other veggeis

    • Grow kohlrabi in the cool part of your year. Weather too warm, too dry, or too wet can cause plants to become stressed. When a plant is stressed it will often not flower and set seed.

    • You can grow kohlrabi whereever there are 45 to 60 growing days (depending upon the variety you grow) where the temperature is below 75F/24C and warmer than 50F/10C. Any cool time of the year will work.

  7. Last year my kohlrabi was destroyed by root maggots in my container pots. Can my kohlrabi plants be covered with a white lightweight crop cover to prevent egg laying? Or would that be too hot for them?

    • Place a lightweight floating row cover over the plants and containers to exclude insects from laying eggs near your plants. A lightweight floating row cover will retain some solar heat around plants. You can lift the cover on very hot days if plants look wilted.

    • If the kohlrabi bulb has broken away from the lower stem, then it’s time to eat the bulb. If the water-conducting capillaries were broken the plant will quit developing. If by broken, you mean the bulb was cut or knocked, the bulb will continue to grow toward harvest.

  8. Hi my cats have broken the stems and the leafs will these still grow as the bulb hasn’t developed yet. The stems are broken just above where the leaves split off on top

    • The kohlrabi “bulb” is a swollen stem; if the stem of the plant has been damaged it is unlikely the plant will go on to produce the swollen stem. Place stakes at the corner of the planting bed and drape bird netting over the stakes and bed to discourage the cats.

  9. I read commentre: flowering. I put in transplants from market mid may. Spikes yellow flowered, bulb large marble size. If I cut back stems can I leave for winter over. Or do
    I not trim back but leave for winter crop. Do I need thick leaf grass cover for this?

    • Kohlrabi is a cabbage-family cousin. It prefers cool weather although it will grow in warm weather–but it will need a lot of water. If the plant has flowered, it is past harvest time. Pull the plant and replant it in early spring or in early autumn. Kohlrabi is a fast grower; you can get a couple of crops in spring and fall. There is no advantage to letting it sit in the garden over the winter; harvest it when it is big enough to eat.

    • Check the days to maturity for each cultivar. If the purples are shorter days to maturity, it may be accountable to temperature; if the temperatures have been warming. Another possible reason is a greater amount of nitrogen in the soil–or more nitrogen fertilizer–where the white kohlrabi is growing. It may take a bit of detective work–but it is like an environmental cause.

    • The best strategy is to take but the bulbous stem and roots and replant seed. This will allow you the most production from your garden.

  10. I planted kohlrabi from seed very early in the spring when it was very cold. The seeds germinated great and made healthy looking little seedlings. I transplanted the seedlings in the garden, but now they will not grow. I started the seeds more than 60 days ago and the entire plant is only one inch. Why?

    • The plants’ roots may have been partially broken or disturbed interrupting growth and stunting the plants. Feed the plants with B1 Vitamin or a dilute solution of fish emulsion or kelp meal (get these at the garden center). In the meantime, plant a second crop where you want it to grow wo it does not need moving.

    • Companion planting is supported by the experience of gardeners and anecdotal evidence. Kohlrabi and melons are not typically considered companions. But, you can plant them close together and see what your experience is.

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