Kohlrabi, a brassica, is unusual for some, less known in the UK than it is on the continent. It is an alien-like crop with a bulbing stem in purple or green and large, edible cabbage-like leaves. This is a useful and versatile vegetable that can be perfect for polytunnel growing. A polytunnel can offer these brassica some protection from slugs, pigeons and other pests. Kohlrabi can be eaten raw or cooked and will fit in well with a brassica rotation in your growing plan.
Sow kohlrabi little and often between around February (indoors) and mid-August (in warmer parts of the UK) in order to get a consistent supply. Cloches or fleece can allow earlier plantings in your polytunnel as well as offering the young plants a little extra protection. Sowing kohlrabi every three weeks is a good rule of thumb for succession planting.
If you live in the colder reaches of the UK, or in an area with heavy, clay soil, it is usually best to sow earlier plantings inside before hardening off and planting out when the weather has warmed sufficiently. Transplant your kohlrabi seedlings before they reach around 5cm in height.
Thin out your kohlrabi seedlings when they are around 2.5cm tall or when the first true leaves have appeared. Leave plants at a final spacing of around 15cm between plants. Keep the soil around you plants consistently moist and weed free, ensuring that the plants do not ever experience a drought.
Kohlrabi plants should be firmed well into a weed-free patch in any reasonably light, fertile and free-draining soil. They will benefit from the addition of a good, organic, nitrogen rich mulch which will add fertility as well as keeping down weeds and keeping in moisture.
Kohlrabi can be harvested from may until around November (in warmer areas). Harvest kohlrabi from when they are the size of golf balls and before they exceed a tennis ball in size for the best flavour. Do not forget that the leaves are also edible and can be used cooked like any cabbage or vegetable green. The kohlrabi can be peeled and grated for use in salads and coleslaw-like dishes. They have a taste a little like a combination between apple and broccoli stem. They can also be cooked like broccoli or mashed and used in a wide range of different recipes.
