David Kopec, Extension Turfgrass Specialist

Scalping occurs when more than 1/3rd of the grass canopy height is removed in any single mowing operation.

Scalping occurs when:

1. A mowing gets "skipped" because of weather conditions

2. Low mowing height selection and infrequent mowing days (or, mowing low, once a week!)

3. Plain old neglect

Scalping causes severe and abrupt changes in turfgrass plants. The sudden defoliation forces new shoots to emerge, in order to make "new leaves" to capture sunlight. The energy to do this comes from root and crown stored food reserves. When you repeatedly scalp, you weaken the grass tremendously. Soon afterwards, the lawn can become very thin, followed by a weed invasion.

Scalping is extremely detrimental to cool season grasses like ryegrass, tall fescue and Kentucky bluegrass.

Bermudagrass doesn't like it much either; however, bermuda will "bounce back" quickly.

Post-Scalping Maintenance:

Bermudagrass

When mowed to low and infrequently, bermudagrass shoots and leaves are often yellow in color. This condition is caused by iron chlorosis, which is caused by the rapid regrowth of new shoots. Adding more nitrogen will only make the condition worse. The remedy here includes (1) spraying iron on the lawn, and (2) raising the mowing height. Mow frequently enough at the raised height so that any further scalping is eliminated.

At higher elevations, Kentucky bluegrass behaves similar to bermudagrass when scalped. A thin-spindly yellow turf often results. Never add nitrogen in the summer to correct this on KBG. Simply raise the mowing heights and add iron.

The grass will grow spindly until it gets accustomed to being mowed regularly, and starts to "fill in."
Bunchgrass lawns with high percentages of ryegrass and tall fescue may simply die from scalping. Re-seeding in the late summer or early fall is then necessary.

So remember - - avoid scalping at all costs.