In theory there is a lot to like about kohl rabi. But it has always remained a bit of a Cinderella crop in the UK and Ireland. I find this slightly strange since it is not difficult to grow, looks pretty astonishing and can be delicious. I think the problem is that it is always described as turnip-like. Turnips, in the UK at last are always associated with poverty, just like lentils. Of course, in Ireland the situation is complicated because ‘swedes’ are called turnips and turnips are called white turnips.
As it goes, kohl rabi is closely related to cabbages and not turnips, being Brassica oleracea Gongylodes Group – gongylodes coming from the Greek for round. The name kohl rabi is from the German kohl cabbage and rabi turnip which is quite logical. It is a popular veg in Germany but also around the world.
It is a quick-growing crop, ready to eat within three months from sowing. Being a brassica it is best in alkaline soils and is subject to a the usual brassica problems. After germination it grows quickly and the stem (not the root) starts to swell quite rapidly if the plants are thinned and kept well watered and fed. To produce a good crop it is important that they grow quickly and are not subject to heat or water stress. Thin them out to 10-15cm apart as soon as they have a couple of leaves so they have room to swell.
They are usually sown from March to June for a succession of crops. As for when to eat them, it is all a load of balls. Most references say to eat them at golf ball size though they can be left to the size of tennis balls. But there are giant kinds that will reach the size of footballs. Except for the giant (‘Superschmelz’) they get very fibrous when large. When pulled, the root end is cut off, along with the leaves and then the stem has to be peeled. The outer rind of the stem has a fibrous layer that needs to be removed. The inside is then sliced, grated or cubed. It has a crunchy texture and a sweet (ish) fresh taste. If you like the stem of calabrese (and we should be eating them) you will like kohl rabi. There are purple-skinned and green kinds and both taste the same. The leaves are edible but because the plants are not that leafy and are quite compact it is not much of a bonus.
So is kohl rabi worth growing? It is not a terribly interesting vegetable, apart from the strange shape. But do not let the constant reference to turnips put you off because turnips, if young and fresh, are a lot better than most people think. They are pretty nutritious too, with lots of Vitamin C. An advantage of kohl rabi is that the edible part is held above the soil, so it is clean and less likely (though not immune) to slug damage. Mealy aphid, a general brassica issue, can infest the growing tip and cause the swollen stem to distort. Overall, it is worth a go and the plants are attractive, so are good in raised beds. If you like your own coleslaw they are very useful.