Iceberg lettuce
Lactuca sativa var. capitata (Crisphead group)
Also known asCrisphead lettuce · Crisphead · Head 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
The most challenging lettuce type for hydroponic growing because it requires specific conditions to form a tight head. EC 0.8-1.5 mS/cm. pH 5.5-6.5. Temperature: 12–18°C (narrower range than other lettuce types; above 22°C, the head doesn't form properly and the plant bolts). Low to moderate light (DLI 12-17 mol/m2/day). From transplant to head harvest: 70-85 days (much slower than loose-leaf lettuce). The tight head formation requires consistent cool temperatures and even light; any stress during head formation causes loose, uneven heads or premature bolting. Tipburn (calcium deficiency at inner leaf margins) is common because airflow can't reach the tightly packed inner leaves. For commercial hydroponic growers, butterhead and loose-leaf types are far more practical than iceberg; the long crop time, narrow temperature requirements, and quality challenges make iceberg unprofitable at small scale. For home growers who specifically want iceberg, grow in the coolest season available and choose varieties bred for hydroponic conditions.
Notable varieties
| Cultivar | Type | Days | Notes |
|---|---|---|---|
| Great Lakes 118 | open pollinated | 80 | 1944 All-America Selections winner that established the modern iceberg type. Solid heads, slow to bolt for an iceberg, more reliable in home gardens than most commercial F1s. Still widely available. |
| Webb's Wonderful | heirloom | 75 | British pre-1890 crisphead, the classic UK summer lettuce. Sweeter than Great Lakes and more bolt-resistant. The supermarket round lettuce most British shoppers grew up with. |
| Crispino | hybrid | 60 | Modern F1 bred for fast heading. Compact, dense heads in two months, useful where the growing window is short. Holds in the field longer before bolting than Great Lakes. |
| Salinas | open pollinated | 80 | The commercial California workhorse for decades. Released by USDA in 1975, named for the Salinas Valley where most US iceberg is grown. Tipburn-resistant under typical field conditions. |