Butterhead lettuce
Lactuca sativa var. capitata
Also known as: Bibb lettuce, Boston lettuce, Butter lettuce
Quick facts
- Category
- leafy greens
- Difficulty
- beginner
- Days to harvest
- 45 to 60 days
- Harvest type
- single harvest then replant
- Spacing
- 20 cm between plants
Environment
- Temperature
- 13–21°C
- pH
- 5.5 to 6.5
- EC (hydroponic)
- 0.8 to 1.4 mS/cm
- Daily light
- 12 to 17 mol/m²/day
Climate and zones
- USDA zones
- 4 to 9 (winter low around -34°C or warmer)
- Frost tolerance
- tolerates light frost
- Season
- cool (spring and fall crops)
Viable growing environments:
- outdoor year-round (in zone)
- outdoor in growing season (annual)
- unheated greenhouse / hoop house
- heated greenhouse
- indoor (heated home)
- indoor hydroponics under grow lights
USDA zone bounds reflect outdoor year-round survival. Anywhere outside the bounded zone range, this crop still grows as an annual in the warm months (outdoor_seasonal), under cover (greenhouse), or indoors under lights.
Growing systems
Butterhead lettuce works in:
- deep water culture (rafts)
- NFT channels
- vertical / aeroponic tower
- media bed (ebb and flow)
- wicking bed
- soil bed
Growing media
The substrate the roots sit in. Choice depends on the system (clay pebbles don't fit NFT channels; rockwool isn't used in media beds) and the crop (butterhead lettuce works in the media listed below).
| Medium | pH effect | Water 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 by source | high | high |
Bacterial surface area matters for aquaponics: clay pebbles, lava rock, and pumice double as biofilter substrate. Low-surface media (rockwool, perlite, pea gravel) work in hydroponics but need a separate biofilter in aquaponics.
Nutrient demand by stage
NPK ratios are relative weights at each growth stage; the nutrient mix calculator scales them to absolute grams or ml. EC targets shift through the plant's life: seedlings need a much lighter solution than fruiting adults.
| Stage | N | P | K | EC target (mS/cm) |
|---|---|---|---|---|
| seedling | 1 | 1 | 1 | 0.6 |
| vegetative | 3 | 1 | 2 | 1.2 |
Aquaponics suitability
Compatible with typical aquaponics nutrient profiles. Fish waste provides enough nitrogen for healthy growth; supplemental potassium, calcium, and iron may still be needed depending on fish stocking density.
Care notes
The standard commercial hydroponic lettuce alongside loose-leaf types. EC 0.8-1.5 mS/cm. pH 5.5-6.5. Temperature: 15–22°C (cool-season crop; above 24°C, bolting begins and leaves become bitter). Moderate light (DLI 12-17 mol/m2/day; excessive light causes tipburn and accelerates bolting). From seed to harvest: 5-7 weeks as heads, 3-4 weeks as baby leaf. NFT, DWC, and raft systems are the standard commercial setups. Tipburn (calcium deficiency at the leaf margins of inner leaves) is the most common quality issue; caused by insufficient calcium transport to fast-growing inner leaves in still air. Improve airflow around heads with fans, and maintain adequate calcium in the nutrient solution. 'Rex' and other tipburn-resistant varieties are preferred for commercial production. For the living lettuce market, harvest the entire plant with root plug attached and package in clamshells. Succession plant weekly for continuous production. Butterhead lettuce is the highest-value lettuce type per head ($2-4 retail per living head), making it the economic foundation of many small commercial hydroponic operations.
Plan a setup with Butterhead lettuce
Verified against: rhs-uk, university-of-arizona-ccac. Last reviewed 2026-05-15.