Cooking kohlrabi | Growing kohlrabi | Site and soil | Sowing | Varieties | Thinning | Watering | Picking | Storing | Troubles
The swollen stems of kohlrabi are not at all familiar either as a garden vegetable or in shops, but it is a very easy vegetable to grow, versatile to cook and pleasantly flavoured. It is a member of the cabbage family, in effect it is a cabbage with a much-thickened stem as opposed to a turnip which has a thickened root. The name is derived from ‘kohl', the german for cabbage and the word for turnip, ‘rabi', in other words ‘cabbage turnip' which aptly describes it.
This vegetable originated in northern Europe in the Middle Ages but it has spread to other countries across the world and it is widely grown in Asia, coping well with warm weather. Under natural conditions, the swollen stem would act as a storage organ, carrying the plant over one winter and into its second flowering and seeding year. In the garden, the stem bases are harvested while still quite small and succulent.
It tends to go over-mature quite quickly and needs to be treated in the same way as its relatives, the radish and the white turnip, both of which get too mature quickly also. It needs no special soil and it is quite reliable under our conditions of climate. It has a sweet turnip-like flavour, but much more delicate and not as hot as turnips can be. It is crunchy when raw but not as hard as turnip. It can be cooked sliced up like turnips, grated like carrots, even the whole bulb cooked when small.
Kohlrabi can be used is a range of ways in the kitchen, similar to turnips. Peeled if necessary to remove the outer skin, it can be boiled or stir-fried in strips, grated for salads or eaten raw like carrots. Kohlrabi is very low in saturated fat and cholesterol, a very good source of dietary fibre, vitamin C, vitamin B6, potassium, copper and manganese. It also contains a series of plant compounds called indoles, which are considered to be valuable natural anti-cancer agents, present in other cabbage-family plants also and not destroyed by cooking.
Site and soil
Kohlrabi is a fast developing crop, ready in about eight to twelve weeks from sowing depending on the time of year and the weather. It needs open soil, rich and fertile and a warm sunny position. It tends to go to seed if the weather is cold in spring.
Because it matures rapidly and can become over-mature quite quickly, kohlrabi needs to be sown at intervals through the spring and summer, like radish. Begin in late March and sow a last batch in early August. Sow the seeds in batches of about five where they are to mature. Just a short row is all that need be sown at one time, spacing the sowing stations about twenty centimetres apart and the rows about thirty centimetres apart, or the same distance from other vegetables. The seeds can be sown more closely to give ‘baby' vegetables, picked small.
The usual varieties are ‘White Vienna' and ‘Purple Vienna' but there are newer kinds such as ‘Lanro', white; ‘Blusta', purple and ‘Quickstar', white which is recommended for an early sowing in a greenhouse or cold frame.
The seedlings should be thinned in two stages to one plant per station. Thinning down to two first and then removing one a week or so later. It is best not to thin down to one seedling immediately in case it is damaged by the thinning or by a snail or pigeon.
Although kohlrabi is quite tolerant of dry soil, better results are achieved if the plants are watered during dry weather.
The little roots can be used at any size, baby size like small beets or larger like garden turnips but generally before they reach the size of a tennis ball because they have tendency to goo woody and fibrous, although this fibre is mostly just below the skin and the stem centre remains crisp.
Just like turnips, and hard-headed cabbage, kohlrabi can be stored into the winter months in a pit, or similar storage, or simply left in the ground although these have a tendency to go woody.
As a member of the cabbage family, the kohlrabi is subject to the usual cabbage family pests, notably cabbage root flies and caterpillars. While the caterpillars damage the leaves, the ‘roots' are perfectly fine to use. It can also suffer clubroot on acidic soils.