Mowing your lawn to 3 inches (8 cm) high will keep it denser and healthier. Photo: http://www.organolawn.com
When I started gardening 50 years ago (yes, I started very young!), we were told the ideal mowing height for a cool-climate lawn was 2 inches (5 cm). This would, we were told, give you the effect of a golf green and who wouldn’t like that?
The problem was low-mown lawns also had huge health problems. They tended to dry out in the summer, were subject to grub damage and filled up with weeds.
We now know that was bad advice. A taller lawn shades the ground and protects its own roots from the burning sun. Also, the root length is roughly proportional to the height of the turf. So short grass has short roots that can’t reach additional water underground in times of drought while a high-mown lawn has long roots that can find deep water if necessary. Many insects that lay their eggs in the soil, especially the beetle species whose larvae are called white grubs, actively seek out short grass; taller blades are obstacles to them reaching the ground. Finally, weed seeds have great difficulty germinating in high turf: sun, essential for their germination, simply doesn’t reach the soil.
So, for cool climate grasses at least, a mowing height of 3 inches (8 cm) is what you should strive for. And most warm climate grasses too.
Leave the golf green look and all its complications to golf courses (they have a whole team of professionals to nurse short lawns through the hard times). If you want a healthy lawn with much less effort, simply mow higher!