This species has been cultivated as a food crop for many hundreds of years and, in that time, several quite distinct forms have arisen. The nomenclature of these forms is confused, to say the least, and by no means universally accepted. We have followed the treatment used by GRIN, though it is very likely to be revised in the future[].

Common Name: Kohl Rabi

General Information

Kohl rabi is an erect, biennial plant derived in cultivation from the wild cabbage. It has a highly shortened stem base that is fleshy and globose. It can grow about 45cm tall.
The plant is often cultivated for its edible swollen stem which can be available almost all year round from successional sowings.

Known Hazards

None known

Botanical References

Range

A cultivated form of B. oleracea, not known in the wild.

Habitat

Not known in the wild.

Properties

Edibility Rating
Medicinal Rating
Habit	Biennial
Height	0.45 m
Growth Rate	Fast
Pollinators	Bees, Self
Self-fertile	Yes
Cultivation Status	Cultivated

Cultivation Details

Kohl rabi originated through cultivation in the warm temperate zone, and can be grown from cool temperate regions to the tropics. It grows best in areas where annual daytime temperatures are within the range 12 - 18°c, but can tolerate 5 - 25°c[]. When dormant, the plant can survive temperatures down to about -2°c, but young growth can be severely damaged at -1°c[]. Very winter hardy, kohl rabi withstands severe frosts and so can be left in the ground all winter in hardiness zones 6 upwards and be harvested as required[]. The young growing plant, however, is sensitive to low temperatures and a week at 10°c will cause the plants to bolt[]. It prefers a mean annual rainfall in the range 900 - 1,300mm, but tolerates 700 - 1,700mm[].
Succeeds in full sun in a well-drained fertile preferably alkaline soil[]. Prefers some shade and plenty of moisture in the growing season[, ]. Succeeds in any reasonable soil, though it is best not grown in an acid soil[, ]. Prefers a pH in the range 6 - 6.5, tolerating 5.5 - 8.5[]. Established plants are drought tolerant but the best stems are formed when the plant does not go short of moisture[, ]. Succeeds in maritime gardens[].
A very fast growing plant, the stems of some cultivars can be harvested 6 - 8 weeks after sowing[].
Yields are normally between 20 - 24 tonnes per hectare[].
The plant is more tolerant of drought and high temperatures than turnips, which it resembles in flavour, and so it is often grown as a substitute for that species[].
There are several named varieties and stem colour can range from white to green and purple[]. Green forms are faster to mature and so more suitable for early sowings, the purple forms are hardier and later to mature, they are used mainly for winter crops[].

Edible Uses

Stem - raw or cooked. The plant produces a swollen stem just above ground level, and this is often used as a root vegetable[]. It has a mild cabbage flavour, when finely grated it makes a good addition to mixed salads and, when cooked, is an excellent vegetable[]. It is best eaten whilst fairly small and tender, between golf ball and tennis ball size. It becomes coarse with age[, , ]. A nutritional analysis is available[].

Leaves - cooked[]. Used as a vegetable, though the quality is not as good as cabbage. The young leaves can also be added to salads, though some people find them difficult to digest. A nutritional analysis is available[].

Medicinal

The leaf is digestive and tonic[].

Agroforestry Uses:

Grows well with onions, beet and aromatic herbs which seem to reduce insect predations[, , ]. Plants also grow well with cucumbers, the roots of each species occupying different levels in the soil[]. Grows badly with strawberries, runner beans and tomatoes[, , ].

Other Uses

None known

Propagation

Seed - sow mid spring to mid summer in situ. Earlier sowings can be made under cloches.