To define a number range, you have to create a new number interval: 1  Specify an alphanumeric key with up to 2 characters. 2  Specify the limits of the number interval.  Mark the number range if it is planned for external number assignment.
3. Trim back the entire plant when it reaches 3 to 6 inches high, or approximately every 10 days. Cut back to within 1 to 2 inches of the ground. Most loose-leaf lettuce varieties grow back from a severe trim to produce more leaves.
Harvesting and Storing Lettuce. Harvest looseleaf lettuce by 2 methods. The best way is to start picking the outer leaves of each plant when they get to be 2 to 3 inches long. Continue picking this way for 4 to 6 weeks until the plant goes to seed (the flower spike grows up out of the center--also called âbolting.â).