Imagine being an LCO (Lawn Care Operator) and doing your best to give a customer (let’s call him Geoffrey) a great lawn. He pays for a seven-step program, aerates and over seeds every few years. He irrigates, too, but Geoffrey’s lawn is stuck in the mediocre category. How could this be? Because he’s a lawn scalper!
“What’s a lawn scalper?” you ponder. It’s exactly how it sounds.
Geoffrey mows his lawn too dang short. He’s a bozo. He has no idea that mowing too short undoes all the good things he and his LCO are doing. He mistakenly believes mowing short buys him a few extra days in case he can’t mow on a seven-day schedule.
Before going any further with this blog, let’s be clear that we’re only talking about cool season turf species, such as Kentucky bluegrass, turf type fescue and perennial ryegrass. And we’re also talking about turf in full sun all dang day. Shady turf is a whole-nother subject! Warm season turf (zoysiagrass and bermudagrass) should be mowed as short as possible (yet another topic). Many of the little mowers are maxed out with a 3-inch height setting. Newer mowers, especially quality brands like Honda and Toro, can be set higher; professional mowers can be set up to at least 4 inches, even 4.5 inches.
Here’s why cool season turf should be mowed as high as possible in the heat of summer. Cool season turf prefers to go dormant in hot and dry weather, but we push it with fertilizer and water, so we can keep it green and growing to enjoy its beauty. The growing point (crown) of cool season turf species is right at the surface of the soil. As such, mowing at LEAST 3 inches high provides a lot of shade at the soil surface, thus keeping the crown reasonably cool. Scalping is defined as anything below 3 inches, and mowing at 2.5 inches should be a felony! Scalped lawns let too much sunshine hit the soil surface, and the heat adversely affects the crown. When the crown of cool surface gets hot, it simply starts to peter out, preferring to go dormant.
In addition to a weak lawn there are a few weeds that always expose the scalpers, prostrate spurge and crabgrass. The weeds germinate because the turf is too weak. The photo below show this well.
There you have it! Cool season turf in full sun should be mowed at 3.5 inches when it’s above 85F. If your mowing service can’t give you 3.5 inches, fire them. If you mow yourself and your old beater mower can’t be raised to 3.5 inches–time for a new one!