Tips on how to grow kohlrabi
These crunchy extraterrestrial-looking brassicas are quick and easy to grow, and have a mild broccoli or cabbage flavour. The swollen stem, which can be purple, red or green, sits above the soil and can be eaten raw in salads or coleslaws, made into fritters, or added to soups and stews.
SOW AND GROW
Sow seeds: August to November and March to May in warm areas; August to November in cooler areas .
Transplant seedlings: August to November and March to May in warm areas; August to November in cooler areas.
Position: Full sun, six or more hours a day.
Harvest: 6-12 weeks from seed. Good for pots and good for beginners.
Like cabbages and broccoli, kohlrabi prefers cooler weather, so sow or plant between early spring and early summer, all over the country. In mild and temperate areas, you can also sow or plant in late summer and early autumn for awinter harvest.
Sow seed direct about 1cm deep and 4cm apart. Germination takes 6–10 days. In 5–6 weeks, thin plants to the strongest specimens, spacing them around 10–25cm apart. Although sowing direct is preferred, if you are short of growing space, you can also start in trays or jiffy pots for transplanting when established.
Prepare the bed with lots of compost and aged manure, a general fertiliser and a little lime. Kohlrabi are a great brassica for small gardens if you don’t have room for cabbages or cauliflowers and can also be grown in pots or 10-litre buckets with holes drilled in the bottom for drainage. Side dress plants with general-purpose fertiliser or liquid feed every two to three weeks to encourage rapid growth.
Harvest the bulbs when they are around the size of a tennis ball. Use a trowel or fork to gently dig them out of the soil. Cut the root and leaves off.
Go for award-winning cabbagegreen ‘‘Grand Duke’’ in smaller gardens, its upright, vigorous growth habit means you can get away with closer spacing. For a fast harvest, try drought-tolerant F1 hybrid ‘‘Emerald’’. For good looks, ‘‘Purple Azure Star’’ and ‘‘Purple Early Vienna’’ both have purple skin and white flesh.
Protect kohlrabi from slugs and snails, especially when young. Cover crops, including trays of seedlings, with horticultural mesh or net curtains to prevent whitefly from sucking out the sugary sap and to prevent white cabbage butterflies from laying eggs on the leaves.
Kohlrabi can be infested by aphids, so spray them off with the hose regularly.
If your plants bolt to seed before the bulbous bases fatten up, it’s almost certainly because they didn’t receive enough water, so keep an eye on irrigation, especially when growing in pots.