Kohlrabi
Brassica oleracea var. gongylodes
Also known asGerman turnip · Turnip cabbage · Stem turnip
Environment
The bounded range this crop tolerates.
Climate and zones
- USDA zones
- 3–10 (winter low around -40°C)
- Frost
- frost hardy
- Season
- cool (spring/fall)
Growing systems
Root mass: moderate.
Growing media
| Medium | pH effect | Retention | Bacterial surface |
|---|---|---|---|
| Expanded clay pebbles (LECA) | neutral / inert | low | high |
| Coco coir (Coconut coir) | slightly acidic | high | moderate |
| Soil-based mix (Potting soil) | varies | high | high |
Nutrient demand by stage
NPK ratios are relative weights. EC targets shift through the plant's life.
| Stage | N | P | K | EC (mS/cm) |
|---|---|---|---|---|
| seedling | 1 | 1 | 1 | 0.8 |
| vegetative | 2 | 1 | 3 | 2 |
Companion-growing notes
- Heavy uptake of potassium, calcium. Co-grown crops with the same demand will end up deficient even at "correct" EC.
Aquaponics suitability
Compatible
Fish waste provides enough nitrogen for healthy growth. Supplemental potassium, calcium, and iron may still be needed depending on fish stocking density.
Care notes
A fast, easy hydroponic crop that's underappreciated outside German and Asian cuisine. Media beds or containers with 10 cm depth (the bulb forms at the surface but roots extend downward). EC 1.5-2.5 mS/cm. pH 6.0-7.0. Temperature: 12–24°C (cool-season; above 28°C the bulb becomes woody and strong-flavored). Moderate light (DLI 14-20 mol/m2/day). From transplant to harvest: 45-60 days for standard varieties, 35-45 for mini varieties ('Kolibri', 'Quickstar'). Harvest when the bulb is 6–10 cm diameter (standard) or 4–6 cm (mini types). Overmaturity causes woodiness and cracking. Mini kohlrabi is gaining popularity with commercial hydroponic growers because it matures faster, produces consistently tender bulbs, and sells well at farmers' markets ($3-5 each) as a trendy, Instagram-friendly vegetable. The leaves are a bonus harvest. Pest and disease issues are minimal compared to heading brassicas. A fun, fast crop for growers who want something different from the standard lettuce-and-tomato lineup.