Name of problem: Scalping
Plant name(s): Turfgrass
Symptoms / Characteristics:
Scalping occurs when grass is cut too short, reducing a lush healthy lawn to a mass of brown stubble. The removal of excess green foliage exposes the crowns, causing the delicate tissue to desiccate and turn brown. The loss of photosynthetic leaf area essentially starves the plants and inhibits root growth. Scalping also encourages shallow rooting. Increased stress renders affected plants extremely susceptible to drought, disease and insect attack. Closely cut lawns are more susceptible to white grub and sod webworm invasions. Furthermore, a sparse lawn canopy facilitates the germination and subsequent invasion of weeds. Scalping can occur when mower blades are set too low, when mower wheels sink into soft ground and when the grass is cut infrequently and severely.
Control / Preventions:
Improper mowing is the leading cause of turfgrass problems. Optimum mowing heights vary according to species and environment but most common turfgrass varieties prefer heights of 6-8 cm. Mowing heights should be raised slightly in shaded areas or during periods of stress. There are two basic rules that must be followed:
(1) never remove more than 1/3 of the foliage at one time
(2) never mow shorter than 5 cm
Following the 1/3 rule may require more frequent mowing but this extra effort will help to eliminate future need for pesticide applications. Mowing at the proper height and frequency will promote healthy, vigorous, more competitive turf. If a lawn has grown longer than usual (e.g. during a vacation or during a period of rainy weather) the grass should be cut in small stages over a period of time so that the target height is reached gradually. Mow when the grass is dry and maintain sharp blades. Scalped turf may recover on its own, depending on the severity of the damage. Heavily damaged areas may need to be reseeded.
Relevant web sites:
McKernan, D. 1994. Great Plains Turfgrass Manual. Patterson Productions, Alberta. 184 pages.
Porter, W.R. 1999. Green Side Up. Fitzhenry & Whiteside, Ontario. 138 pages.