Lettuce
Also known as
Garden lettuce, Head lettuce, Leaf lettuce, Butterhead lettuce, Cos lettuce, Romaine
Keep this plant’s care guide close at hand.
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Lactuca sativa, commonly known as lettuce, is a cool-season annual grown primarily for its tender, edible leaves and, in some types, compact heads. It includes diverse cultivar groups such as leaf, romaine (cos), butterhead, and crisphead, each differing in texture, flavor, and growth habit. Plants have shallow, fibrous root systems and prefer fertile, well-drained soils rich in organic matter. Lettuce grows best in cool temperatures, producing crisp, mild leaves; heat accelerates bolting (premature flowering) and can cause bitterness. Most varieties mature quickly, typically within 30–70 days from sowing depending on type and season. Regular, even moisture is essential to prevent tip burn and maintain sweetness. Lettuce can be grown in beds, raised planters, containers, and hydroponic systems. It is generally tolerant of light frosts, especially at the seedling stage, but sustained freezing or high heat reduces quality. Common pests include aphids, slugs, and snails; diseases include downy mildew and bottom rot, mitigated by good spacing, airflow, and crop rotation.
Taxonomy
Properties & Requirements
How to care for Lettuce
Water
Keep the root zone consistently moist but never waterlogged. Aim for about 2.5–3.8 cm of water per week from rain and irrigation, adjusting for heat and wind. Water in the morning to dry leaf surfaces quickly and reduce disease; try to irrigate at soil level for heading types. In containers, check daily—shallow roots dry fast. Use mulch to moderate evaporation and prevent soil splash. Allow only the top 1–2 cm to dry between waterings.
Light
Provide full sun in cool seasons (6+ hours daily). In warm climates or late spring, give morning sun and afternoon shade to keep plants cool and delay bolting. Indoors, supply 12–16 hours of bright light; under LEDs, moderate intensity prevents legginess without overheating. Insufficient light yields weak, floppy growth; excessive midday sun in heat stresses plants. Maintain good airflow to keep leaf surfaces dry, especially under high light.
Nutrients
Incorporate 2–5 cm of well-aged compost before planting to boost organic matter and moisture retention. Apply a balanced, nitrogen-forward fertilizer (e.g., 4-4-4 to 5-5-5) at planting, then side-dress with a light nitrogen source (e.g., blood meal, fish emulsion, or 10-10-10 at one-third rate) 3–4 weeks later. Avoid heavy, late nitrogen that promotes soft growth and nitrate accumulation. Maintain soil pH near 6.2–6.8 and steady moisture for consistent nutrient uptake. In hydroponics, target EC 1.2–1.8 mS/cm and pH 5.8–6.2.
Temperature
Lettuce prefers cool conditions: ideal growth occurs at 10–21°C. Germination is best around 16–21°C and slows markedly above 24°C. Prolonged temperatures over 24–26°C with long days promote bolting and bitterness; provide afternoon shade and ample moisture in warm spells. Seedlings and many varieties tolerate light frosts, but hard freezes can damage leaves. For indoor or greenhouse culture, maintain 16–20°C days with slightly cooler nights for compact, crisp growth.
