Planting Guide and Seed Saving Notes for Kohlrabi
Kohlrabi (Brassica oleracea)
Kohlrabi seems to take its shape from alien spacecraft. A pale green or deep purple stem plumps up into a perfect globe that sits atop the soil line and leaves radiate off, ready to take flight. Harvest the whole plant by slicing the tap root just at the soil line and separate the leaves from the globe for storage. Both parts can be eaten the leaves cooked like collards or cabbage, while the bulbous stem is excellent shredded for slaw, roasted, baked, mashed, or curried.
Nutrients: dietary fiber, vitamin C, potassium, phytochemicals.
How to Grow Kohlrabi from Seed
Kohlrabi is a cold hardy vegetable that prefers full sun and fertile, well-drained soil. Before planting, incorporate 2-4 inches of well-composted organic matter
Kohlrabi seed can be started indoors 4-6 weeks before the last frost in spring or in mid-late summer for a fall harvest. Sow seeds ¼-1/2" deep and 2-4” apart. Seeds will sprout in 5-17 days. Thin seedlings so that mature plants are 8-12" apart. Transplant seedlings outdoors when plants are about 6 wk old or have 3-4 true leaves.
Kohlrabi can also be direct seeded with optimal germination at soil temps of 50-80˚ F. When sowing outdoors for a fall crop, plan for a harvest about two weeks after the first frost date.
Kohlrabi is ready to harvest in 55-65 days after planting. Harvest by cutting tap root at soil line just below bulb. Best eaten when the bulbs are under 3" to preserve taste and texture.
How to save Kohlrabi Seed
Kohlrabi is an insect pollinated biennial that doesn't flower and set seed until the following season. Leave ½ mile between the plants you want to save the seed of and any other Brassica oleracea to prevent crossing. The Brassica oleracea family is large, so be extra careful of what you have growing out to seed around you. After flowers have turned to seed pods, leave the seeds to mature and dry on the plant as long as possible before gathering. Once plant material is so dry it crumbles at your touch, carefully put the dry pods in a bag and process.