Kohlrabi is an odd-looking member of the cabbage family grown for its bulb-like stem that tastes like a mild, sweet turnip. You can also eat the leaves. High in fiber and vitamin C, kohlrabi is a fast-growing cool-weather crop, with plants ready to harvest just a few weeks after planting. Try growing kohlrabi in spring or fall.
Soil, Planting, and Care
Set out spring plants about 4 weeks before the last frost so they mature in cool weather. Plants just out of a greenhouse need initial protection from freezes. Set out fall plants about 6 weeks before the first frost. In fall, plants “hardened” by gradual exposure to cool weather are tolerant of frost. Kohlrabi that matures in cool weather is deliciously sweet.
Kohlrabi needs at least 6 hours of full sun each day; more is better. Give it fertile, well-drained, moist soil with plenty of rich organic matter. A soil pH between 6.5 and 6.8 discourages clubroot disease. To check pH, test the soil with a purchased kit, or get a soil test through your regional Cooperative Extension office. Fertilize and lime according to test recommendations.
Without a soil test, add nitrogen-rich amendments such as blood meal, cottonseed meal, or composted manure to the soil. Or, work a timed-release vegetable food such as 14-14-14 into the soil according to label directions. Also use liquid starter fertilizer such as fish emulsion or Bonnie Herb & Vegetable Plant Food at planting for a boost. Fertilize with a liquid fertilizer again after plants begin to develop new leaves and when they start forming heads. Space plants 9 to 12 inches apart.
Kohlrabi needs an even supply of moisture to produce good bulbs. Mulch with compost, finely ground leaves, or finely ground bark to keep the soil cool and moist and to keep down weeds. Apply 1 to 1.5 inches of water per week if it doesn’t rain. You can measure the amount of water with a rain gauge.
Although the same pests that like cabbage can also attack kohlrabi, it is generally less troubled by aphids, root maggots, cabbageworms, and other caterpillars. Clubroot and black rot diseases in the soil can be a problem.
Harvest and Storage
Harvest kohlrabi stems when they are still young and tender, usually about 2 1/2 to 4 inches in diameter. Harvest by cutting them from the base of the plant. You can trim the leaves from the stem and save them to cook separately. Kohlrabi keeps for 2 to 3 weeks in the fridge. You can peel and slice kohlrabi tubers to eat them raw with dips or in salads, or you can cook them like turnips. The leaves are cooked until just tender, like cabbage or turnip greens.
Is there a secret to growing great kohlrabi?
Does kohlrabi need a lot of water?
How can I keep weeds under control without damaging the plants?
The kohlrabi I have picked so far are tough and bitter. What is wrong?
Can I eat the leaves of kohlrabi?
They’re calling for frost tomorrow night. Do I need to pick the kohlrabi?