General
Lettuce (Lactuca sativa) is a cool-season leafy crop valued for crisp, tender leaves. Types include looseleaf (fast, cut-and-come-again), butterhead (soft heads), romaine/cos (upright, crunchy), and crisphead/iceberg (tight heads, slow). It thrives in cool weather (10–18°C), can tolerate light frost, and tends to bolt and turn bitter in heat. For a continuous supply, sow small amounts every 2–3 weeks and mix types and maturities.
Light
Full sun to partial shade; prefers cool conditions with morning sun and light afternoon shade in summer.
Soil type
Moisture-retentive, fertile, well-drained loam enriched with compost.
Water requirement
Keep evenly moist; about 25–30 mm per week. Avoid drought and waterlogging. Water early in the day, ideally via drip or at soil level.
Nutrient requirement
Moderate feeder; steady, modest nitrogen. Overfeeding causes soft growth and tipburn.
Precultivation
Sow indoors 3–5 weeks before planting out. Use 10–16°C for germination; higher temperatures can cause dormancy. Transplant sturdy seedlings with 3–4 true leaves. Harden off for 5–7 days before planting. For head types, raise in modules to precise spacing; for looseleaf/baby leaf, you can multi-sow 3–5 seeds per cell and thin by harvesting.
Planting
Plant out when daytime temperatures are consistently above 5–7°C and soil is workable. Space: looseleaf 20–25 cm between plants, 25–30 cm between rows; butterhead 25–30 cm; romaine 30–35 cm; crisphead 30–40 cm. Plant shallowly so the crown sits just above soil level. Mulch lightly after the soil has warmed to stabilize moisture and temperature.
Pruning
No pruning required. For looseleaf, harvest outer leaves regularly to maintain airflow. Remove any yellowing lower leaves to reduce disease.
Maintenance
Keep soil evenly moist; mulch with straw or leaf mold. Side-dress with compost or a light organic nitrogen source 3–4 weeks after planting. Use fleece or cloches in early spring/autumn for frost protection, and shade cloth (30–40%) in warm spells to reduce bolting. Hoe lightly to control weeds; shallow roots are easily damaged. Rotate away from other Asteraceae and leaf crops for 3–4 years.
Harvest
Baby leaves: 25–35 days; harvest by cutting above the crown for regrowth. Looseleaf: pick outer leaves continuously. Butterhead/crisphead: cut whole heads when firm and full size (45–70 days). Romaine: harvest when hearts are elongated and crisp. Harvest early morning for best quality, cool immediately, and store at 0–4°C with high humidity.
Common issues
Bolting and bitterness in heat—use shade, steady moisture, and bolt-resistant varieties. Tipburn from uneven moisture and rapid growth—maintain consistent watering and moderate nitrogen. Slugs/snails—use beer traps, copper barriers, hand-picking, and habitat for predators. Aphids—wash off with water, encourage beneficials, use soft soap if needed. Downy mildew and leaf spots—ensure spacing, water at soil level, grow resistant cultivars, rotate crops. Damping-off in seedlings—use clean trays, good airflow, and avoid overwatering.
Rotation schedule
Rotate on a 3–4 year cycle. Avoid planting after lettuce or other Asteraceae (endive, chicory). Follow heavy feeders (e.g., cabbage family) with lettuce to use residual fertility, then follow lettuce with legumes or root crops. Keep beds weed-free and incorporate compost before planting.
Pollination
Self-pollinating when flowering, but typically harvested before flowering; wind can aid pollen transfer.
Companion plants
Carrot, radish, onion, garlic, chive, cucumber, strawberry, dill, marigold, calendula, peas.
Incompatible plants
Parsley, celery, sunflower; avoid strong-rooted heavy feeders that outcompete moisture.
