Butterhead lettuce
Lactuca sativa var. capitata
Also known asBibb lettuce · Boston lettuce · Butter lettuce
Environment
The bounded range this crop tolerates.
Climate and zones
- USDA zones
- 4–9 (winter low around -34°C)
- Frost
- tolerates light frost
- Season
- cool (spring/fall)
Growing systems
Root mass: light.
Growing media
| Medium | pH effect | Retention | Bacterial surface |
|---|---|---|---|
| Rockwool (Mineral wool) | alkaline until pre-soaked | very high | low |
| Expanded clay pebbles (LECA) | neutral / inert | low | high |
| Coco coir (Coconut coir) | slightly acidic | high | moderate |
| Net pot, no medium (Bare-root) | - | - | - |
| 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 | 0.6 |
| vegetative | 3 | 1 | 2 | 1.2 |
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 standard commercial hydroponic lettuce alongside loose-leaf types. Hold EC around 0.8-1.2 mS/cm and pH 5.5-6.5. It is cool-season, best at 15–22°C; above 24°C it starts to bolt and turns bitter. Keep light moderate, 12-17 mol/m2/day, since too much light raises tipburn and hastens bolting. Heads are ready in five to seven weeks from seed, or three to four as baby leaf, in NFT, deep water culture and raft systems. Tipburn is the main quality problem: a localised calcium deficiency in the fast-growing inner leaves, because calcium moves almost only through the xylem on the transpiration stream and barely reaches those low-transpiration inner leaves in still air. Move air around the heads with fans, keep calcium adequate in the feed, and favour tipburn-resistant varieties like Rex for commercial work. For the living-lettuce market, harvest the whole plant with its root plug and pack in a clamshell. Sow weekly for continuous production.