Kohlrabi grows as a bulb topped with a rosette of long-stemmed blue-green leaves, making it a very odd looking vegetable. It can be white, green, or purple and has a mild taste that has made it popular in dishes from salads to soups.
Kohlrabi is grown for its swollen base which is actually the plant’s stem and makes it look like a turnip growing on a cabbage root. Kohlrabi is milder and sweeter than either cabbage or turnip and both the globe base and leaves can be eaten. The globe-shaped base develops above the ground making Kohlrabi a good choice for gardens that don’t have deep soils.
Kohlrabi is a hardy biennial grown as an annual. It is a cool-weather crop and should be sown in the garden 3 to 4 weeks before the last average frost date in spring. It grows best in cool temperatures between 4.4°C and 23.9°C and requires 45 to 60 days to reach maturity. In warm winter regions, Kohlrabi should be sown in late summer for a winter harvest. It can withstand an early autumn frost and should be planted in full sun.
For best results, grow Kohlrabi in well-worked, well-drained soil rich in organic matter. Work 2 to 5cm of aged compost into the soil before you begin planting. Seeds can be started indoors, in a cold frame or plastic tunnel. Kohlrabi requires 45 to 60 days to reach maturity and should be grown so that it comes to harvest before temperatures average greater than 23.9°C.
In hot summer areas, you should plan for an autumn harvest. In warm winter regions, you can grow Kohlrabi through the winter. Kohlrabi should be sown in late summer for a winter harvest. Kohlrabi can withstand an early autumn frost. In cold winter regions, sow kohlrabi in summer for early autumn harvest. You can sow kohlrabi seeds as long as temperatures are greater than 4.5°C.
If you are growing kohlrabi for late autumn or winter harvest, protect plants with row covers or a plastic tunnel if night time temperatures below -4°C are predicted. Sow kohlrabi seed 8mm deep and 2.5 cm apart. Thin successful seedlings to 20cm apart. Space rows 45-60 cm apart. Thinned seedlings can be transplanted to another part of the garden. Grow 6 to 10 plants per person. Companion plants. Beets, celery, herbs, onions, potatoes. Do not plant with pole beans, strawberries or tomatoes.