Robin Gale-Baker, from Sustainable Macleod, discusses growing kohlrabi. This is one of a series of articles she has written about growing herbs and veggies (see right hand sidebar). She has also written a number of articles about growing fruit trees and general growing techniques.
What is kohlrabi?
Kohlrabi is easy to grow, crops twice a year and is delicious raw or cooked. There are two types of kohlrabi in Australia – white (or light green) and the princely purple. Both grow a bulb about the size of a tennis ball above the soil, and the leaves emanate from this bulb in a sculptural fashion. Kohlrabi has a sweet taste and crisp texture.
How to grow kohlrabi
Kohlrabi can be planted in punnets or directly into the ground and later thinned. It is a prolific germinator and, for this reason, planting directly will give it a head start and avoid transplant shock. Kohlrabi is planted a month before the last expected frost in spring, and in late summer for a winter crop. It likes cool weather and is frost tolerant. In fact, frost can make it taste sweeter. Choose a position that receives 6 full hours of sun a day and is well drained, moist, and rich in organic matter. The pH needs to be between 6–6.8. Plant the seed 1cm deep and space 10–15cm apart in rows which are 30–45cm apart. Planting too closely will result in the bulbs not forming so thinning is essential if the seed is directly sown. Other reasons for bulb failure are poor soil, nutrient deficiencies or inadequate watering. Bulbs mature in 45–60 days. Bad companion plants include capsicums, climbing beans, peas, strawberries and tomatoes so avoid planting within 2 metres of these. Good companions include onions, cabbage species (of which they are one), cucumbers and beetroot/silverbeet.
Pests common to kohlrabi
As a member of the cabbage species, kohlrabi plants need protection from white cabbage butterfly. Fine netting secured at the bottom to completely enclose the plants works best. Slugs and snails are also a nuisance and will largely be kept out by netting but some snail bait will deal with any intruders. Look out for aphids too on the stems and backs of leaves and spray with soapy water until ladybirds arrive to devour them.
How to use kohlrabi
Whether raw or cooked, kohlrabi needs to be peeled as the skin is fibrous. The bulb is delicious raw as a main ingredient, paired with crisp apple in a salad, or as a crunchy, additional ingredient in a mixed salad. Cooked, it goes well in stir fries and can be roasted in a variety of ways. The leaves (including the thinnings) can be eaten in salads or used as a spinach or silverbeet in soups, pies or even pesto.