Kohlrabi

You grow kohlrabi as an annual: you harvest the bulbs in the same season in which you sow. It does not overwinter in the bed. Bring the bulbs in before the first hard frost; late varieties can stay outdoors a little longer under horticultural fleece or a layer of leaves. Harvested bulbs stay fresh for a few days if kept cool and moist; for longer, blanch and freeze them, and sow anew next spring.

Kohlrabi is propagated exclusively by sowing. You can start it from mid-February indoors or in a greenhouse: sow the seeds about 0.5 to 1 cm deep in seed compost; at 16 to 20 °C they germinate in about 6 to 12 days. After around four weeks, when the young plants are strong, harden them off outdoors for about ten days (out during the day, in at night) before planting them in the bed from mid-March to April. Direct sowing outdoors is possible from April/May, as soon as the soil has warmed to at least 10 °C. Sow about 1 cm deep with rows about 25 to 30 cm apart, and thin later to 15 to 20 cm. Staggered sowings from February into summer extend the harvest over many weeks. Important: if the young plants stand too cool for a longer time (about 5 to 12 °C), you risk early bolting instead of bulb formation. After germination, keep them bright at 14 to 18 °C instead.