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.
To sow lettuce directly in the garden, simply plant the seeds about 1/4 inch deep, tamp them down, and water. It's that simple! Space the sowings according to packet directions that are based on the size of the mature lettuce. For example, a crisphead may require a square foot of garden space.