This close relative of the cabbage was bred over centuries to develop a flattened "meristem" over a taproot that descends into the soil. Sometimes referred to as German turnips, kohlrabis are very rich in vitamin C, and a great source of potassium. The flavour is like a very mild cabbage and the texture is crisp and crunchy, a bit like that of a pear. Great in salads or eaten raw. Continue reading to learn how to grow kohlrabi from seed.
Brassica oleracea var. gongylodes
We Recommend: Kolibri (KH434). We don’t recommend this wonderful hybrid kohlrabi for any other reason than how splendid looking it is in the garden. Kolibri has the same fine flavour and texture as Kongo, but hey – it’s bright purple! More gardeners need to grow familiar with this nutritious, easy-to-grow vegetable.
Season & Zone
Season: Cool season
Direct sow several times during the four to six weeks after the last frost date for a crop to mature starting in about 8 weeks. Sow again after mid-July to early August for fall and winter crops. Planting between mid-May and mid-July causes kohlrabi to mature in hot weather, resulting in inferior bulbs. In short season areas, start kohlrabi indoors in cell trays about 4 weeks before the last frost date and transplant out once day time temperatures are steadily above 10°C (50°F). Optimal soil temperature for germination: 10-30°C (50-85°F). Seeds should germinate in 7-10 days.
Sow seeds 5mm (¼”) deep with plants spaced 10-15cm (4-6″) apart in rows 30-45cm (12-18″) apart.
Days to Maturity: From direct sowing.
Ideal pH: 6.0-6.8. Kohlrabi is a moderate to heavy feeder that does best in humus-rich soil amended with composted manure. Mix ¼-½ cup complete organic fertilizer into the soil under each plant.
Spring-sown kohlrabi will get larger than tennis balls in fair soil, but if you pick them when they are still less than 5-8cm (2-3″) in diameter they will be sweet and tender. Fall-grown kohlrabi can grow larger yet stay tender. Kohlrabi is frost-hardy, and may last well beyond Christmas in mild winter areas.
In optimal conditions, at least 80% of the seeds will germinate. Usual seed life: 3 years. Per 100′ row: 360 seeds, per acre: 104M seeds.
Diseases & Pests
Protect from cabbage moths and other insect pests with floating row cover. Prevent disease with a strict 4-year crop rotation; avoiding planting Brassicas in the same spot more than once every four years.
A worthy companion for beets, Brassicas, cucumbers, and onions. Avoid planting near peppers, pole beans, strawberries, and tomatoes.
More on Companion Planting.