Collard greens
Brassica oleracea var. viridis
Also known asCollards · Tree cabbage · Borekale · Couve
Environment
The bounded range this crop tolerates.
Climate and zones
- USDA zones
- 6–11 (winter low around -23°C)
- Frost
- very hardy (survives deep cold)
- 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 | 3 | 1 | 2 | 2 |
Companion-growing notes
- Heavy uptake of 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
An easy and productive hydroponic leafy green that tolerates both heat and cold. EC 1.5-2.5 mS/cm. pH 6.0-7.0. Temperature: 15–30°C (one of the few brassicas that performs well in warm conditions; also handles cold down to about -5°C). Moderate to high light (DLI 14-22 mol/m2/day). DWC, NFT, or media bed systems work. The plants are large (60–90 cm tall) and need more space than lettuce or bok choy. From transplant to first harvest: 6-8 weeks. Harvest lower leaves progressively (cut-and-come-again), leaving the growing tip and upper leaves to continue production. A single plant provides harvests every 1-2 weeks for months. The thick, sturdy leaves hold up to long cooking (the traditional method) but can also be eaten raw in salads or massaged with oil and salt for a kale-salad-style preparation. Caterpillars (cabbage loopers, imported cabbageworm) and aphids are common pests; BT spray controls caterpillars. For aquaponics growers, collards are a reliable, low-maintenance, long-producing green that handles the temperature fluctuations of outdoor and semi-outdoor systems.