Mowing: Never More Than 1/3 at a Time
When you mow the lawn, never remove more than one third of its length at a time. Cutting it back too severely will weaken it. Typically, if you want to maintain turf at a healthy height of 2 1/2 to 3 inches (6.5 to 8 cm), mow when grass is 4 or 5 inches tall.
If you’ve gotten a bit lazy or were away on vacation and your grass reaches 6 inches (15 cm) in height or more, it’s not a good idea to immediately mow it back to 3 inches (8 cm). Instead, stick to the one-third rule: cut the grass to two thirds of its height, wait 2 or 3 days, then mow again at the desired height. If the grass is very high, 8 inches (20 cm) or more, you may need mow the lawn 3 or even 4 times, gradually lowering the height each time.