Growing Lettuce

Spring/Fall (cool season): Any variety works. Butterhead types (Buttercrunch, Skyphos) produce tender, premium heads. Romaine types (Little Gem, Parris Island) are sturdy for salad bags. Red varieties (Red Sails, Outredgeous) add color and typically have more anthocyanin antioxidants.

Summer (heat management): Choose bolt-resistant varieties: Jericho (romaine, bred for Middle Eastern heat), Muir (slow-bolting butterhead), Concept (resistant loose-leaf), and Green Star. Leaf lettuce bolts later than head types. Provide 30-50% shade cloth. In tropical climates at low elevations, lettuce is best grown October-March or year-round under shade structures at 40-50% shade.

The secret to continuous lettuce supply is succession planting - sow a new batch every 2-3 weeks throughout the growing season. Each planting produces for 3-4 weeks (loose-leaf with cut-and-come-again) or provides a single head harvest (butterhead, romaine). Overlapping plantings ensure you never face a gap in production.

Sow seeds 1/4 inch deep in trays or direct-sow in beds. Lettuce needs light to germinate - do not bury seeds deeply. Optimal germination temperature is 60-68°F; above 80°F, germination drops dramatically (a condition called thermodormancy). In hot weather, start seeds in a cool location or refrigerate moistened seeds for 2-3 days before sowing. Germination takes 2-7 days. Transplant or thin to final spacing when seedlings have 3-4 true leaves.

Lettuce has shallow roots and thrives in rich, moisture-retentive soil. Amend beds with 1-2 inches of compost. Lettuce does not need heavy fertilization - moderate nitrogen promotes leaf growth without the bitter taste excess nitrogen can cause.

Spacing depends on type and harvest method: Baby leaf mix (cut-and-come-again): Broadcast seed densely (1/2 inch spacing) in 4-inch-wide bands; harvest at 4-6 inches tall by cutting 1 inch above the crown. Full-size loose-leaf: 6-8 inches apart. Butterhead/Romaine heads: 8-12 inches apart. Iceberg: 12-15 inches apart. Dense spacing is the norm for market production - lettuce grows well close together and dense planting shades the soil, reducing weed pressure and maintaining moisture.

Bolting is triggered by: temperatures above 80°F, long days (14+ hours of light), and water stress. Once a lettuce plant starts to bolt, it cannot be reversed - the center elongates, leaves become bitter, and quality drops rapidly. Prevention strategies:

Shade: 30-50% shade cloth reduces leaf temperature by 10-15°F and delays bolting by 2-3 weeks. In tropical climates, shade is essential for lettuce production. Timing: Plant so that the harvest period falls during the cooler parts of the season. Variety selection: Slow-bolt varieties (Jericho, Muir, concept) can extend the season by weeks. Consistent watering: Drought stress accelerates bolting - keep soil evenly moist. Mulch: Keeps roots cool, which delays bolting. Harvest promptly: Pick at peak size; waiting for "one more day" often means the plant bolts overnight.

Loose-leaf lettuce varieties can be harvested multiple times using the cut-and-come-again method: cut leaves 1 inch above the crown when they reach 4-6 inches tall. The growing point remains intact and regrows a new flush of leaves in 10-14 days. You can get 2-4 cuttings from a single planting before the plants decline or bolt.

For head lettuce (butterhead, romaine), harvest the entire head by cutting at the base with a sharp knife. Leave the root in the ground - some varieties will sprout small secondary heads from the stump, providing a bonus harvest. For maximum freshness and shelf life, harvest in the early morning when leaves are turgid with water. Immediately cool harvested lettuce by plunging in cold water, then spin dry and refrigerate.

Spring: Direct sow as soon as soil can be worked (lettuce tolerates light frost). Use row cover for protection and warmth. Summer: Shade cloth, bolt-resistant varieties, and frequent succession planting. Harvest early and often. Fall: The best lettuce season - cooling temperatures produce tender, sweet leaves. Plant heavily for fall markets. Winter: Low tunnels, cold frames, or unheated greenhouses (high tunnels) allow lettuce production through winter in zones 5+. Lettuce survives temperatures down to 20°F under protection.

In tropical climates, lettuce is a dry-season crop (November-March in most locations). Year-round production requires shade houses (sarán) at 40-60% shade, drip irrigation, and heat-tolerant varieties. Hydroponic lettuce production (NFT or raft systems) is increasingly popular in tropical areas where soil-based production is difficult due to heat and disease pressure.