A cool-season crop that grows well in the spring and fall in most regions, lettuce is perfect for beginners as it’s easily sown by seed directly in the soil as soon as the ground can be worked. Given lettuce grows quickly, it’s best to plant a small number of seeds at a time, staggering the plantings. It’s an excellent leafy green given they grow quickly, produce for a long time, and aren’t particularly demanding as long as the plants are sufficiently watered.
Planting and Growing Information:
Lettuce prefers a location with 5 to 6 hours of sun, but it can also benefit from afternoon shade when temperatures increase. Soil should be loose, well-draining, and have a slightly acidic to neutral pH. Soil temperatures should be between 45°F and 65°F. Meanwhile, cold-adapted varieties can survive much lower temperatures. Direct sowing is recommended. Be sure to plant seeds in the ground 2 to 4 weeks before your last spring frost date, or as soon as the ground can be worked. To get a head start, begin seeds indoors about 1 month before your last spring frost date. Before setting indoors, harden off seedlings for 3 days to a week. If you’re purchasing transplants (small plants), you may plant between 2 weeks before your last spring frost to 2 weeks after your last spring frost. It’s possible to plant another crop of lettuce in the fall or even early winter in most regions.
Given the seed is so small, a well-tilled seedbed is essential, and stones and large clods of dirt will inhibit germination. Plant seeds to ⅛ to ¼ of an inch deep. To germinate, lettuce needs light, so don’t sow them too deep. Seeds may be sown in single rows or broadcast for wide row planting (loose-leaf varieties are best for this). When broadcasting, thin 1- to 2-inch-tall seedlings for the proper spacing. Spacing between plants depends on the variety. For loose-leaf lettuce, plant or thin to 4 inches apart. For romaine (cos) and butterhead (loose-head, Bibb, Boston) lettuce, plant or thin to 8 inches apart. For crisphead (iceberg) lettuce, plant or thin to 16 inches apart. Make sure to set rows of lettuce 12 to 15 inches apart. For a continuous harvest, sow additional seeds every 2 weeks. Water thoroughly with a mist nozzle at the time of transplanting or seeding. For a fall crop, cool the soil in August by moistening it and covering it with a bale of straw. A week later, the soil under the bale should be a few degrees cooler than the rest of the garden and ready to be sown with a 2-foot row of lettuce. Every couple of weeks, repeat the process by rotating the straw bale around the garden. Seed as usual for a fall harvest as autumn temperatures decline.
You can help transplants along at the start of the season by covering them with a temporary cloche made from bottomless milk cartons or plastic bottles. By doing this, it will keep the chill off your seedlings just enough to help them acclimatize. Freshly planted lettuces could also be helped with a simple row cover or fleece. Ensure the soil remains moist but not overly wet, and it should drain well. Overwatering leads to disease or soft growth. Lettuce will let you know when it needs water. If the leaves are wilting, sprinkle them anytime, even in the heat of the day, to cool them off and slow down the transpiration rate. To prevent lettuce from drying out in the sun, using row covers can help. Organic mulch will aid with conversing moisture, suppressing weeds, and keeping soil temperatures cool throughout the warmer months. If necessary, weed by hand, but be careful not to damage your lettuce plants’ shallow roots.
Bolting is a common problem that’s a result of warm temperatures (over 70°F) or changes in day length. When a lettuce plant bolts, it begins to produce a central stem and seed stalk, causing the leaves to taste bitter. To delay bolting, cover plants with a shade cloth so they receive filtered light. Also make sure to maintain watering throughout the warmest parts of the growing season. To help reduce bolting in the heat of the summer, plan your garden so that lettuce will be in the shade of taller plants, such as tomatoes or sweet corn.
Weeks prior to planting, amend soil with plenty of compost for added fertility. Fertilize as often as every 2 weeks with a balanced water soluble or granular fertilizer, such as a 10-10-10, which prevents the lettuce from becoming bitter and allows it to continue to grow.
Harvest lettuce in the morning when full-size but young and tender. Be sure to check your garden every day for ready-to-harvest leaves as mature lettuce becomes bitter and woody and will quickly go bad. Before reaching maturity, you may harvest leaf lettuce by simply removing the outer leaves so that the center leaves can continue to grow. To harvest butterhead, romaine, and loose-leaf types, remove the outer leaves, dig up the entire plant, or cut the plant about an inch above the soil surface. It’s possible to have a second harvest when using the first or third methods. Meanwhile, crisphead lettuce is picked when the center is firm.