Brassica oleracea, Gongylodes Group: Once a common vegetable, this curious brassica family crop had fallen into unfortunate obscurity, only recently being rediscovered by many present-day gardeners. Its crisp, mildly sweet bulb has a hint of apple, can be enjoyed raw or cooked, and provides lots of fiber, vitamins C and B6 along with copper, potassium, and manganese.
Days to maturity are calculated from date of transplant.
• Kohlrabi performs best in the cool season and can tolerate a wide range of soil types
• For extended harvests, plant every 2-3 weeks
• Mature plants are frost tolerant and cool weather brings out sweet flavor
• May and June sowings should be avoided as they result in kohlrabi maturing in the hottest weather, producing dry, woody bulbs
• Sowings can resume from mid-July to mid-August for fall/winter harvest
• Thin when plants have 2 sets of true leaves
• Start seeds 4-6 weeks before anticipated transplant date
• Transplant outside when there are 6-8 true leaves and nighttime temperatures remain above 40°F
• Start May—July for transplanting June—August for a fall crop
Insects & Diseases
• Common insects: See Brassica Insect Information below
• Disease prevention: 5-7 year crop rotation
Harvest & Storage
• For spring-sown kohlrabi: harvest when less than 2-4 inches in diameter
• Fall-grown kohlrabi is less likely to get woody as it gets larger
• Store at 36°F and 95% relative humidity
Brassica Insect Information
Aphids: Control aphids with ladybugs or a hard spray of water or Pyrethrin. Also, select varieties that mature later in the season when aphid populations decline.
Cabbage worms, loopers, and root maggots: The first sign of cabbage worms will be off-white butterflies fluttering near the plants. They lay their yellowish-colored eggs on the undersides of leaves, which hatch into caterpillars that can cause severe root and head damage. To control light infestations, spray plants with Bacillus thuringiensis (B.t.). For heavy infestations, bait cabbage worms by mixing wheat bran into a B.t. solution. Add 1 tablespoon of molasses. Broadcast the bran mixture around the base of plants. Reapply as necessary. Using Reemay or Summer Insect Barrier can also provide control.
Flea beetles: Flea beetles chew tiny pinholes in leaves. Early control is essential to minimize the damage. Spray infected plants with Pyrethrin. Using floating row covers such as Summer Insect Barrier can also provide control.
Symphylans: In some areas of the US, symphylans (also known as garden centipede) can severely impede the plant growth of many crops. Only 1/4 inch long, white, and very active, they eat the root hairs of developing plants. Using larger transplants helps reduce damage. Contact your local county extension agent if you suspect you have a problem.