Kohlrabi

Kohlrabi is grown for its swollen stem, harvested while still tender and crisp. Its rapid growth suits it to succession sowing and to filling short gaps in vegetable rotations, and it can be grown in spring, autumn, and, in mild areas, over winter.

Steady, uninterrupted growth is the key to quality: stress or slow growth makes the stem woody and fibrous, so consistent moisture and fertility are emphasised.

Family

Brassicaceae (cabbage or mustard family)

Botanical name

Brassica oleracea (Gongylodes group)

Growth habit

Biennial forming a swollen edible stem above ground, topped by long-stalked leaves; bolts to flower under stress or in its second year

Relatives

The same species as cabbage, broccoli, cauliflower, and kale

Kohlrabi was developed in Europe from the wild cabbage lineage that gave rise to the diverse Brassica oleracea vegetables, and it is grown widely across Europe, Asia, and other temperate regions, being particularly popular in parts of central Europe and South and East Asia.

Because it is a fresh vegetable, detailed production statistics are limited; available figures are compiled by FAO and national agencies and should be consulted directly.

Kohlrabi is a cool-season crop that grows best in mild conditions and is moderately frost-hardy, making it suitable for spring and autumn cropping and, in mild climates, winter production. Its fast maturity allows it to be fitted into short growing windows.

Exposure of young plants to prolonged cold can trigger premature bolting, so sowing timing is chosen to avoid cold checks during establishment.

Kohlrabi grows best on fertile, moisture-retentive, well-drained loams with a firm seedbed. As with other brassicas, a soil pH that is not too acidic helps reduce the risk of clubroot, an important soilborne disease of the family.

Kohlrabi is direct-seeded or transplanted, in successional sowings for a continuous supply. Rotation away from other brassicas and attention to soil pH help manage clubroot and other shared problems, and steady growth is maintained for quality.

• Successional sowing or transplanting for a continuous supply
• Rotation away from other brassicas to manage clubroot and shared pests
• Firm, fertile, moisture-retentive seedbed and steady growth for tender stems
• Timely harvest before the swollen stem becomes woody

Kohlrabi responds to fertile soils, with adequate nitrogen supporting rapid growth and balanced nutrition contributing to firm, tender stems. As a brassica, it can be sensitive to deficiencies of nutrients such as boron on some soils.

Consistent moisture is important to keep kohlrabi growing steadily and to prevent the stem from becoming woody or splitting, and irrigation is used where rainfall is insufficient. Uneven watering can cause growth checks and cracking of the swollen stem.

Clubroot, a soilborne disease causing swollen, distorted roots, is a major constraint on kohlrabi and other brassicas, managed largely through rotation, drainage, and soil pH. Downy mildew, damping-off, and bacterial diseases such as black rot also affect the crop.

Flea beetles pit the leaves of young plants, and aphids (including the cabbage aphid), caterpillars, cutworms, and cabbage root fly also damage the crop. Management combines rotation, protection such as netting, sanitation, and, where warranted, locally authorized controls applied according to their labels.

Kohlrabi is harvested by cutting the swollen stem while it is still tender, typically at a young, moderate size before it becomes woody, though some modern types remain tender at a larger size. Trimmed stems are cooled and marketed, and young leaves can also be used.

• Swollen stem eaten raw, grated or sliced in salads and slaws
• Stem cooked in soups, stir-fries, roasts, and braises
• Young, tender leaves cooked as greens
• A fast, space-efficient vegetable for gardens and market production