This is the million dollar question. Brummel Lawn does our spring cut (first cut of the year) at 3” and rest of the season we mow at 3.5”. We don’t change up our heights very often due to the fact that it is very difficult to change on the large commercial mowers. We run mowers that have fixed decks vs the floating decks. With the fixed deck it takes the variables out of setting the mowing height by having to adjust anything onsite. The front wheels are set and we just have to put 2 spacers on each blade. Our current mowers run with three 18” blades but only cut a 52” path. During seeding season, early fall we will drop the height down to 3”.
On freshly seeded lawns (complete renovations) the first mow should be done at 2.5” and will help simulate the grass to grow. This is only if it is a complete lawn, if it’s just an over seeding the normal mowing level will be fine.
On newly sodded yards we recommend waiting as long as possible, the longer the grass is on the top normally the longer the roots are in the soil. If it has gotten too long bagging might need to be done.
Brummel Lawn doesn’t recommend bagging as the cuttings offer free nitrogen to the turf. Without bagging your lawn, your lawn can get up to 1 additional pound of nitrogen. The general rule of thumb is not to cut more that 1/3 of the grass off, but with the springs and only cutting one time per week this doesn’t always happen. Double cutting helps prevent cuttings from sitting on the top of the lawn is done. Besides the additional nitrogen you receive by leaving the cuttings you also will get a thicker lawn, by getting some thatch. I know in the fall everyone talks about de-thatching, and so on, but some thatch is good to ensure a healthy lawn. As long as you don’t have more than ¼” of thatch you are in great shape!
In early spring leaf cleanup we lower our deck to 2-2.5” to help get the ground up leaves up and also to cut the tops of the grass off to speed up greening up the lawn.
So to recap the right height at the right time:
Early Spring (even as early as Feb) 2-2.5”
Spring (April) 3”
Late Spring and Summer 3.5” (if it gets really dry every other week)
Early Fall (During Seeding Season) 3”