From
the Experts at Simplicity®
Often cutting height is a matter of personal
preference. Typically, you should mow the grass when
it is between three and five inches high. The proper
cutting height range for a specific lawn will depend
upon several factors, including the type of grass,
the amount of rainfall, the prevailing temperature,
and the lawn's overall condition.
Cutting the grass too short causes weak, thin grass
plants, which are easily damaged by dry periods and
pests. Cutting too short is often more damaging than
allowing the grass to be slightly higher.
Letting grass grow a bit longer–especially when
it is hot and dry–reduces heat build-up, preserves
needed moisture and protects the grass from heat
damage and other problems. However, allowing grass
to grow too high can cause thin turf and additional
problems.
Cutting off too much at one time shocks the
plant's growth system and weakens the grass plants.
A good rule of thumb is the 1/3 rule: to cut no more
than one third of the grass height, and never more
than 1 inch at a time.
The amount of grass you are able to cut in one
pass is also effected by the type of mowing system
you are using (for example, broadcasting with side
discharge decks can process a much larger volume of
grass than mulching does).