Kohlrabi

Thrives in USDA Zones 3 - 9

• Start Indoors

  4–6 weeks before last frost date

• Transplant

  2–4 weeks before last frost date in spring; 6–8 weeks before first fall frost

• Direct Sow

  2–4 weeks before last frost date; or late summer for fall crop

• Harvest

  Cut bulbs at soil level when 2–3 inches in diameter; larger bulbs become woody and fibrous

• Side-dress with compost or worm castings when bulbs begin to swell to fuel rapid sizing without excess nitrogen that promotes leaves over bulb

• Mulch with straw or shredded leaves to retain soil moisture and keep roots cool; inconsistent watering causes cracked, pithy bulbs

• Apply diluted compost tea every 2–3 weeks to support steady, even growth and strengthen resistance to aphids and cabbage worms

• Use floating row cover from transplant to harvest to exclude cabbage moths, imported cabbageworms, and flea beetles without any sprays

• Rotate kohlrabi with non-brassica crops on a 3–4 year cycle to reduce clubroot and other soil-borne brassica diseases

• Interplant with onions or nasturtiums as a companion planting strategy shown in traditional kitchen gardens to deter aphids and whiteflies

• Watering

  If the top 2 inches of soil feel dry, a deep watering at the base may help more than frequent light watering. In healthy soil, rain may cover much of what it needs.

• Feeding

  If growth is strong, compost-rich soil often carries most of the load. If the plant starts looking pale or stalls, a light compost top-dressing or gentle organic feed may help.

• Seasonal care

  During the main season, harvesting when the crop is ready and removing damaged growth can help keep the planting productive if it starts to look crowded or tired.

• Harvest timing

  Harvests often cluster around April, May, June, September, October, November. If fruit, leaves, or roots start looking ready, color, size, firmness, and scent usually tell you more than the calendar alone.

• Early White Vienna

  A classic open-pollinated pale green variety that matures in about 55 days with a mild, tender bulb; one of the most widely grown heirloom kohlrabis in home gardens.

  Best for

  Spring and fall crops, seed saving, all-purpose kitchen use

• Early Purple Vienna

  Identical in flavor and texture to White Vienna but with striking purple skin; the flesh inside remains white and the purple color deepens in cool weather, making it visually distinctive at market.

  Best for

  Ornamental kitchen gardens, fall crops, fresh eating

• Kolibri

  A reliable F1 hybrid purple kohlrabi that matures quickly around 45 days, holds its tenderness at larger sizes than heirloom types, and resists bolting better than open-pollinated varieties.

  Best for

  Short-season gardens, succession planting, reliability in variable spring weather

• Superschmelz

  A giant heirloom variety that can grow to 8–10 inches in diameter while remaining sweet and tender, unlike standard varieties that become pithy when oversized; particularly popular in German-speaking Europe.

  Best for

  Long-season growing, storage, feeding a family from a small number of plants

• Cabbage worms
• Imported cabbageworm
• Flea beetles
• Aphids
• Cabbage loopers
• Slugs
• Harlequin bugs

Origin

Kohlrabi is a cultivated form of Brassica oleracea developed through selective breeding in European gardens, derived from wild ancestors native to the coastal Mediterranean and Atlantic regions of Europe.

Native Habitat

The wild progenitor of Brassica oleracea grows on rocky coastal cliffs and sea bluffs in western Europe, particularly along the Atlantic coasts of Britain, France, and the northern Mediterranean, where thin, well-drained soils and cool maritime conditions prevail.

Current Distribution

Kohlrabi is cultivated worldwide as a cool-season vegetable crop, with particular popularity in Central and Northern Europe, South and East Asia, and North American home and market gardens; it does not naturalize outside cultivation.

Kingdom

Plantae

Family

Mustard family (Brassicaceae)

Genus

Brassica

Species

Brassica oleracea var. gongylodes

• Root System

  Shallow fibrous roots spread close to the soil surface, making kohlrabi sensitive to cultivation or hoeing near the plant base; keep the area mulched rather than cultivated to avoid root disturbance.

• Stem

  The edible part is a greatly swollen, globe-shaped stem internode that forms just above the soil surface; leaf scars left as outer leaves are removed make the bulb look knobby and are completely normal.

• Leaves

  Blue-green to purple leaves emerge from the top of the swollen bulb on long petioles; yellowing lower leaves are a sign of nitrogen stress or overcrowding, while powdery or mottled leaves suggest fungal infection or aphid damage.

• Flowers

  If allowed to bolt under heat or long days, kohlrabi sends up a tall flower stalk with small yellow brassica-type flowers; bolted bulbs become woody and inedible, so remove plants that send up flower stalks.

• Fruit

  The primary edible structure is the stem bulb, harvested before it exceeds 3 inches in diameter; seed pods resemble small slender siliques typical of brassicas and can be saved from isolated, open-pollinated plants for seed propagation.

Kohlrabi is one of the many cultivated varieties of Brassica oleracea, the same highly plastic species that gave rise to cabbage, broccoli, cauliflower, and kale through centuries of selective cultivation in Mediterranean Europe. The swollen stem that defines kohlrabi is thought to have been developed in northern European gardens by the fifteenth or sixteenth century; the botanist Matthioli described it in 1554, and it spread rapidly through German, Austrian, and Bohemian kitchen gardens. The name derives from the German Kohl (cabbage) and Rabi (turnip). Unlike turnip, the edible bulb forms above ground, making it easier to harvest in wet or clay soils where root crops struggle.

Kohlrabi has not figured prominently in formal medicinal traditions and is documented primarily as a food plant. European herbalists from the sixteenth century onward noted it mainly in the context of kitchen cultivation rather than therapeutics. Historical interest in the brassica family more broadly centered on cabbage leaves and seeds rather than kohlrabi specifically.

• Early modern European herbalism, 16th century - bulb

  Matthioli's 1554 herbal described kohlrabi as a garden curiosity eaten cooked or raw by Italian and German populations, noting it was thought to be nourishing and easy to digest compared to heavier root vegetables.

• Central European folk tradition, 17th–19th century - leaves and bulb

  In German and Bohemian households, kohlrabi leaves were used alongside the bulb in simple broths prepared for convalescents, reflecting a broader European pattern of associating cooked brassica vegetables with mild, restorative eating during illness.

Kohlrabi is safe for most people as a food plant. Individuals on anticoagulant medications should be aware that brassica vegetables contain vitamin K. Those with thyroid conditions sensitive to raw goitrogenic foods may wish to consult a physician about large quantities of raw brassicas.

This information is provided for historical and educational purposes only and is not medical advice. Always consult a qualified healthcare professional before making decisions related to your health.