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.
Grow It: Sow seeds for leaf mixes thickly, preferably using a seeder, in tight rows 2 to 3 inches apart in 4-foot-wide beds. Cut leaves off one plant up to four times, tasting every time to make sure it hasnât become too bitter. For head lettuce, sow or transplant seeds 10 to18 inches apart, depending on the variety.