Scalped Lawns


Mid summer is when one starts to see more scalped lawns, or lawns that are habitually cut too low and begin turning brown. I will discuss WHY this happens (both plant and people) and WHY it is a poor cultivation/management technique. First, the height you choose for mowing should be determined by the (1) type of grass and (2) conditions. Bent grass, like you find on golf putting greens, can be trimmed as low as 1/2-inch but that is not the grass most of us use for a lawn. Instead, our lawns mostly are some sort of bunch or sod grass and the recommended cutting height for most types is never less than 2.5-inches, but that does not stop 3/4+ of all homeowners from scalping. Moreover, our lawns are usually a mixture of several different species, although some among us insist on trying to create and maintain a sterile looking monoculture (i.e., a chemical dependent rug--I do not use or advocate this practice). As regards conditions, most new homes sites have had all the good native and vital topsoil removed by the "developer" so the owners have to deal with a clayey substitute which is slow to drain when wet, brick hard when dry and if sloped even less likely to retain moisture in dry weather.

Why is a scalped lawn bad? Scalping stresses the grass--makes the lawn less drought tolerant, sometimes killing it. Root development corresponds to (i.e., is about coequal with) the amount of above ground growth. It is the plant roots that do the most to aerate and improve the organic content of this "soil." Moreover, when the plants are scalped there is less photosynthetic capacity (i.e., the plant has trouble making enough food to feed itself); it is actually bad for the plants, both physically and physiologically. Scalped lawn soil also (1) gets more sunlight allowing it to dry out more quickly and (2) promotes weed species germination and growth--perfect for many of our most troublesome lawn weeds (e.g., plantain, dandelion, knotweed, etc.). And, since soil temperature is regulated by water content, a drier organically impoverished soil is subject to profound temperature swings (fever and chills) and is less conducive to optimal lawn/turf development.

So, why do most people scalp? (1) wanting to reduce the number of mows and/or (2) unwilling or unable to adjust their mower setting. I have also occasionally encountered people who like the brown scalped look. I do not.

Additional lawn/mowing recommendations:

1. Never remove more than 1/3 the total grass height with any one mow

2. Keep the mower blades sharp (promotes cutting rather than tearing and reduces mower stress)

3. Cut shady areas higher and/or less often

4. Alter the pattern to prevent unwanted directional matting

5. Do not mow when the soil is saturated (see also my Dec 2016 rant)

6. In addition to being worse for the plants, a low mower setting increases the chance of hitting and damage to and from low lying objects

7. If a lawn does not receive on average 1-inch of water a week (depending on factors discussed above) it will start to go dormant and scalped lawns are slower and less likely to recover from dormancy--FYI: for a 1/4-acre space this equates to nearly 30,000 gallons of water or more than two days of continuous flow from a spigot with normal output (about 8-gallon per minute)--expensive, unnecessary and usually inadequate, and finally

8. Consider having less lawn, while mowing higher and less often, and go easy with the chems

I discuss addition factors regarding lawn, grass and mowing in Rantings of a Mad Botanist, especially chapters 33 & 45

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