Easy to grow and fun to eat, kohlrabi deserves a place in your lineup of cold-tolerant spring vegetables. Pushed along by days that are getting longer and warmer, spring-sown kohlrabi seedlings quickly grow into crisp, juicy above-ground bulbs. And while they are not a true root vegetable, trimmed kohlrabi will store in the refrigerator for weeks or even months, just like carrots, radishes and beetroot.
The upright plants with their grey-green leaves combine well with other vegetables that grow in the same mini season of mid spring to early summer. Spring cabbage, green onions from sets, radishes and kohlrabi are ready in early summer, a little ahead of peas. You will need to grow fast-maturing kohlrabi varieties like purple Kolibri, Delicacy Purple or Early Purple Vienna, green Kongo or Winner, or perhaps white Beas, bred in Northern India and popular for its mild flavour and tender skin.
![Kohlrabi seedlings under grow lights]()
Kohlrabi seedlings started indoors make good growth under lights
Start Seeds Under Lights
Kohlrabi seeds germinate so quickly that they are suitable for use as edible sprouts. Seeds sown in moist seed starting mix with a pinch of vermiculite on top (to retain surface moisture) germinate in five to seven days at room temperature. As soon as the seeds sprout, move them to bright grow lights, or use a red/blue LED light turned on 12 hours a day. If the seedlings flop a bit, add pinches of dry seed starting mix around the base of the stems while increasing light and ventilation.
![Kohlrabi seedlings]()
Kohlrabi seedlings toughen up quickly when exposed to filtered sun and light wind
Harden Off Seedlings
Gradually accustom indoor-grown kohlrabi seedlings to sun and wind by hardening them off in an opaque plastic bin (with the lid off) or other protected spot for at least a week. The tender leaves sunscald easily, so it’s important to increase their light supply a little at a time. While the seedlings are hardening off, prepare their planting space by digging in plenty of rich organic compost or a balanced organic fertiliser, following label rates. Use row cover tunnels or milk carton cloches to protect plants from cold winds and help them settle in quickly.
![Kohlrabi mulched with grass clippings]()
Green kohlrabi mulched with spring grass clippings
Mulch with Grass Clippings
The first grass clippings of spring are extra high in nitrogen, so they make an ideal mulch for fast-growing kohlrabi. Grass clippings also contain trace amounts of boron, a micronutrient for which cabbage family crops have an above-average need. Any organic mulch, including rough compost or weathered leaves, will conserve soil moisture and insulate the roots from hot or cold conditions at the surface.
![Cross-striped cabbageworm]()
Cross-striped cabbageworm damage to a kohlrabi leaf
Watch for Pests
Kohlrabi is sometimes bothered by cabbage worms, though the flat, linear leaves offer few places to hide compared to broccoli, kale or cabbage. Of more concern is the cross-striped cabbageworm (Evergestis rimosalis), a recent arrival in many American gardens. Unlike green cabbageworms, which lay single eggs, this species lays eggs in masses, so numerous caterpillars appear at once. Pick them off by hand.
![Kohlrabi and garlic scapes]()
Spring kohlrabi matures in early summer, at the same time as garlic scapes
Harvest Promptly
With remarkable uniformity, spring kohlrabi will swell up all at once, 50 to 60 days or so after transplanting. While it’s tempting to wait for the bulbs to grow larger, the best quality kohlrabi is harvested at 2 to 3 inches (5 to 7 cm) in diameter. Kohlrabi left in the garden too long can become woody, and overgrown bulbs are prone to splitting after heavy rains.
![Kohlrabi and sage costar]()
Kohlrabi and sage co-star in a savoury spring casserole
Trimmed of leaves and roots and wiped dry, kohlrabi will store in perfect condition in plastic bags or containers in the refrigerator for several weeks. This gives you plenty of time to try recipes like kohlrabi fries, or perhaps a savoury casserole with sage or other spring herbs. Many of the oldest recipes call for pairing cooked kohlrabi with a cream sauce, accented with nutmeg. As other spring vegetables start coming in, kohlrabi can be combined with spring onions, garlic scapes, spinach, and the first early peas in stir fries or grain bowls. This is garden to table eating at its best.
