How to Grow Kohlrabi From Seed

Kohlrabi is a fast, cool-season crop, so aim for the mild ends of the year. Sow in early spring, about 2 to 4 weeks before your last frost, for a spring crop, and again in late summer for a fall crop, which tends to be the sweetest and most tender. Because White Vienna is ready in only about 50 to 55 days, you can sow small batches every couple of weeks and tuck it in around slower vegetables.

Kohlrabi grows so fast that it is best direct-sown right where it will grow. Sow the small seeds a quarter to half an inch deep in rich, well-drained soil in full sun, keep the bed evenly moist, and expect sprouts in 5 to 10 days. Thin the seedlings to 4 to 6 inches apart so each plant has room to swell its bulb, in rows about 10 to 12 inches apart. Even spacing and steady moisture give the tenderest bulbs.

Kohlrabi is easy if you keep it growing fast and steady. Give it about an inch of water a week so it never checks, and a light feed to push quick, tender growth. The eating part is the swollen stem that forms just above the soil, so do not hill soil over it. Watch for flea beetles and cabbage worms and use row cover on young plants. In hot regions, grow kohlrabi in fall, winter, and early spring, since summer heat makes bulbs woody and can trigger bolting; in cool-summer areas it grows through much of the season.

Kohlrabi shares a bed happily with plants that pull pests away and bring in helpful insects. These four make especially good neighbors, and you can add any of them in one click:

Harvest when the swollen bulb is about 2 to 3 inches across, roughly tennis-ball size. Cut it off at the base with a knife rather than pulling, and trim off the leaves (save the tender ones to cook). Do not wait for a bigger bulb, since size past that point comes at the cost of texture. In fall you can leave bulbs in the ground a little longer, as light frost does not hurt them.

Kohlrabi tastes like a sweeter, milder broccoli stem. Peel off the tough skin and eat the crisp inside raw in sticks or slaw, roast or saute it, or drop it into soups and stir-fries. The tender leaves cook up like kale or collards. Homegrown White Vienna, picked young, is juicy and sweet enough to eat out of hand in the garden.

• Woody bulbs: from harvesting too late or from heat and drought. Grow in cool weather, water evenly, and pick at 2 to 3 inches.
• No bulb forming: usually crowding, heat, or dry soil. Thin to 4 to 6 inches, keep it moist, and grow it in the cool season.
• Flea beetles: tiny holes in young leaves. Cover seedlings with row cover and plant radishes nearby as a trap crop.
• Bolting: heat makes plants flower instead of bulbing. Time the crop for cool weather and favor spring and fall sowings.