General Info: Lettuce is a cool loving, fast growing, leafy annual that does not like high heat or direct summer sun. It tastes best when grown quickly in moist, fertile, mineral-rich soil.
Seeds: Small, black or white seeds shaped like arrowheads. Seeds store for 3 years and germinate in 6 -12 days.
Varieties: Hundreds of varieties that fall generally into the following categories:
- Loose-leaf – good for multiple harvests of leaves and in mesclun mixes
- Romaine/cos – heat-tolerant long firm heads
- Summer Crisp/Batavian – looser crispy heads
- Crisphead – tight iceberg type heads – needs long growing season
- Butterhead – soft loose heads – more tender
Create your own mixtures. Choose hardy winter varieties (Winter Density) to sow in the fall.
Indoor Sowing: Sow indoors in planting mix, 2 seeds per container during late winter and early spring. Harden off and transplant when seedlings are 2″ tall at 2″-3″ spacing in rows or blocks. Keep some seedlings handy during the summer to interplant wherever there is shaded space.
Outdoor Sowing: Direct seed small amounts in the garden or greenhouse from spring onwards every 2-3 weeks until late September. Sow seeds about 1″ apart in 8″-12″ rows or thinly (1 seed per square inch) all over a 2-foot square block.
Sow on the surface and cover with a light dressing of soil (less than 1/2″). Water gently and protect with a floating row cover.
In hot summers, put seeds in the fridge for 1 week and pre-sprout in a damp paper towel in a sealed plastic bag.
Soil: Prefers rich, slightly alkaline fertile soil, high in humus and nitrogen. It will tolerate poorer soils if mulched and fertilized well; use alfalfa pellets or soybean meal for additional nitrogen. Till the top 3″ of soil to a fine texture and add compost.
Cultivation: Keep the soil evenly moist; water through the row cover until seedlings are strong and to keep them cool. Spray the leaves with cool water if they wilt but not in the afternoon/evening. Use shade cloth or lattice over the plants to reduce heat.
Thin the plants as needed (see harvesting) without disturbing the roots. Mulch the soil if there is room around the plants. Interplant on the north or east side of taller shade-giving plants such as beans, tomatoes and broccoli.
Harvesting: Loose-leaf types – crop the leaves when they are 4″-6″ high, cutting them off 1.5″ off the soil. For all types – crop the larger outer leaves or cut out thinnings for use. Leave 6″ space around heading types and allow to grow until fully formed. Stop lettuce bolting by pinching out the center shoot.
Nutritional Value: Lettuce, though high in water is an excellent source of chlorophyll, vitamin A, vitamin K, folate, vitamin C, manganese, iron and chromium. It is high in dietary fiber and minerals.
Home-grown organic lettuce has more than twice the mineral and sugar (brix) levels of ‘organic’ hydroponic-grown lettuce you find in Whole Foods. Of course, it tastes much better.