NFT
Hydroponic Kohlrabi: Growing Above-Ground Bulbs in Water Culture
Complete guide to growing kohlrabi hydroponically. Learn variety selection, timing for tender bulbs, and harvesting techniques for this unique brassica vegetable.
Introduction to Hydroponic Kohlrabi
Kohlrabi (Brassica oleracea var. gongylodes) is the overlooked gem of the cabbage family, forming crisp, sweet bulbs above ground that taste like a mild broccoli stem. Hydroponic cultivation produces exceptionally tender kohlrabi in just 45-60 days.
Understanding Kohlrabi Growth
Unlike true root vegetables, kohlrabi's edible bulb is actually a swollen stem that forms above the growing medium. This makes it ideal for hydroponic systems as no deep containers are needed. Leaves are also edible and nutritious.
Variety Selection
- Purple varieties: Purple Vienna, Kolibri - beautiful color, slightly sweeter
- Green varieties: White Vienna, Kossak, Winner - milder flavor, faster growing
- Giant varieties: Superschmelz, Gigante - can reach 10+ lbs without becoming woody
Hydroponic System Selection
NFT systems work excellently as kohlrabi's above-ground bulb doesn't need root space for bulb development. Dutch buckets and deep water culture also work well. Any system supporting leafy brassicas suits kohlrabi.
Growing Conditions
Cool season crop preferring 60-70°F. Tolerates down to 40°F and up to 75°F. Higher temperatures cause woody texture and bolting. Light: 12-16 hours daily at 300-500 µmol/m²/s. pH: 6.0-7.0 optimal.
Nutrient Requirements
Similar to other brassicas: N 150-200ppm, P 50ppm, K 200ppm, Ca 180ppm, EC 1.8-2.4. Calcium and boron critical for preventing hollow stems. Sulfur (50-80ppm) enhances flavor.
Timing for Tender Bulbs
The key to tender kohlrabi is harvesting at the right size. Standard varieties: harvest at 2-3 inches diameter. Giant varieties can grow larger without becoming woody. Overmature bulbs become fibrous and tough.
Common Problems
- Woody texture: Heat stress, water stress, or overmature harvest
- Cracking: Irregular watering or nutrient fluctuations
- Hollow stems: Boron or calcium deficiency
- Bolting: Temperature stress or long days after cold exposure
Harvesting
Cut bulb at base when it reaches target size. Leaves can be harvested earlier as cooking greens. Store refrigerated for 2-3 weeks. Bulbs can be eaten raw (sliced/grated) or cooked.
Related: Root Vegetables Guide
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