Whether your lettuce will regrow when you cut it depends on the type of lettuce in question. It also depends on the weather, and when you cut the lettuce within its growth cycle.
Lettuce comes in five types: leaf, crisphead, butterhead, romaine (also called cos), and stem. Leaf lettuce will grow back up to three times if you cut it, according to plant expert and nursery owner Rose Marie Nichols McGee.
Lettuce is temperature sensitive, and quickly turns bitter and goes to seed when temperatures get too hot. Therefore, to successfully trim your leaf lettuces and have them regrow, you must plant early enough in the spring to have time for the lettuce to grow back after you trim it. Check with your local county extension office for the best planting times for your area.
Called "cut-and-come-again harvesting" by Rose Marie Nichols McGee and the University of Maryland College of Agricultural and Natural Resources, cut your leaf lettuce with sharp shears when it reaches 6 to 10 inches high. Water and fertilize it to harvest again in two to three weeks. Stagger harvests and seed sowing to have a continual harvest before cool spring turns into hot summer.