Harvesting Lettuce to Promote Growth

Lettuce Types

• Lettuce comes in three main types -- head lettuce, romaine and leaf. Head lettuce, which includes the crisphead and butterhead types, forms a dense head suitable for only one harvest at maturity. Romaine, or cos, lettuce forms a loose, upright head and is also only suitable for a single harvest. The leaf lettuce varieties, which produce many loose, crisp leaves, can continue to grow over a several months with frequent harvesting. The harvesting delays seed formation, which allows a single lettuce plant to produce additional edible leaves.

Harvest Method

• Leaf lettuce produces new inner leaves, with the older leaves moving to the outside of the plant. Frequently harvesting these outer leaves encourages the plant to continue producing new inner leaves until it bolts, or sets seed. The leaves are ready for picking when they grow 3 to 6 inches tall, which usually takes fewer than 35 days from germination. Cut these outer leaves off at the base with shears, leaving the inner foliage in place to continue growing. Alternatively, cut the whole plant back to within 3 inches of the ground when it's 6 to 8 inches tall and allow it to grow back before harvesting again.

Continued Care

• After the initial harvest, leaf lettuce needs continued care to continue producing. Continue to water the lettuce about once weekly, supplying enough water to moisten the top 6 inches of soil during each irrigation. You can increase productivity and encourage more leaf growth by supplying the lettuce with 1/4 cup of a 21-0-0 fertilizer blend to every 10 feet of row, working it into the top 2 inches of soil about 6 inches away from the base of the plants.

Bolting

• When leaf lettuce bolts, it becomes bitter and unpleasant. Preventing bolting can extend the harvest. Generally, warm temperatures above 80 degrees Fahrenheit cause bolting. Stress, such as from drought, can also cause the plants to set seed. Growing lettuce during cool weather and providing sufficient water can delay bolting. Mulching over the soil with 2 inches of straw helps retain moisture and keeps the soil cool. Frequent harvest when the leaves reach sufficient length provides another method to prevent bolting and increase productivity.