Kohlrabi

Brassica oleracea var. gongylodes

The part you eat is a swollen stem, a crisp ball just above the soil. It tastes like a mild, sweet cabbage. Kohlrabi grows fast, so sow a short row every few weeks from spring to late summer, not all at once. Pick it young, because a bulb left to grow big turns woody.

Looking after it

Water: Kohlrabi needs normal watering. Keep the soil evenly moist, because dry spells slow growth and make the bulbs tough. Water young plants regularly until they are well rooted. Feeding: Average feeding is enough. Dig in compost before sowing and mulch once plants are growing. It needs less nitrogen than other cabbages, so you don't need to give extra feed.

Harvest and keeping

Cut the stem below the bulb when it is between golf-ball and tennis-ball size. You can cook the young leaves like kale. Cut off the leaves and the root. In a plastic bag in the fridge it keeps 2 to 4 weeks.

What can go wrong

Cabbage caterpillars. Green caterpillars eat holes in the leaves. Cover plants with fine insect mesh. Or look under the leaves for eggs and caterpillars and pick them off.
Flea beetles. In warm, dry weather young leaves get lots of tiny round holes. Keep seedlings watered and cover them with fine mesh until they are big and growing strongly.
Woody bulbs. The flesh turns tough and stringy after hot, dry weather or when you pick too late. Water in dry spells and pick before the bulb is bigger than a tennis ball.

Growing facts: RHS, UC ANR and seed-company sowing guides. Kohlrabi care: RHS. How many to grow: Kansas State and University of Missouri extension. pH: University of Connecticut and University of Maryland extension. Keeping: University of Missouri extension.