Sound mowing practices are necessary for a good quality lawn. This is especially true during the summer months. Improper mowing during hot, dry weather may seriously damage the turf.
Mow Kentucky bluegrass lawns at a height of 3 to 3 1/2 inches during the summer months. During cool weather in spring and fall, bluegrass lawns should be mowed at a height of 2 to 2 1/2 inches. The additional leaf area during summer shades and cools the crowns of the turfgrass plants. Extremely high temperatures at crown level can kill turfgrass.
When mowing the lawn never remove more than one-third of the total leaf area at any one time. A lawn mowed at a height of 3 inches should be cut when it reaches a height of 4 1/2 inches. Removing more than one-third of the leaf area weakens the turfgrass and reduces its capacity to withstand additional environmental stresses. Weakened turf is also more likely to be invaded by weeds.
If possible mow in the cool of the morning or evening. Mowing during high temperatures of midday places additional stress on the turf. Also make sure the mower blade is sharp. Dull blades tear and bruise the leaf tips.
Gardeners have two basic options on lawn care when confronted with hot, dry weather. One option is to simply allow the turf to turn brown and go dormant. The alternate is to properly water the lawn to maintain green turf during dry weather.
Kentucky bluegrass lawns can survive extended periods of drought by going dormant. Most healthy lawns can survive in a dormant state for 4 to 6 weeks without rainfall or irrigation. Healthy lawns that have been allowed to go dormant will green up again when the turf receives sufficient water.
Gardeners who want a green lawn throughout the summer should water the lawn when symptoms of moisture stress begin to develop but before the grass becomes dormant. A good indication of water stress in turfgrass is leaf color. The normally green leaves become a dull blue-green. Additionally, water-stressed turfgrass is less resilient. Footprints remain in the turf after walking across it.
Turfgrass requires approximately 1 to 1 1/2 inches of water per week. The actual amount of water required depends upon soil type and weather conditions. When irrigating turfgrass the general rule of thumb is to water deeply but infrequently. A thorough soaking (which moistens the soil to a depth of 8 to 10 inches) once a week is much better than frequent light waterings. Deep watering promotes the development of deep extensive root systems. Deeply-rooted turfgrass can withstand stressful weather conditions much better than shallow-rooted plants.
Sprinklers are the best way to water lawns. The amount of water applied may be estimated by placing several straight-sided cans in the spray pattern and then measuring the amount of water in the cans with a ruler.
The best time to water a lawn is early morning. Winds are generally light and temperatures cool so little water is lost through evaporation. Watering at midday is less efficient because evaporation is often high and strong winds may cause uneven water distribution. Strong midday winds may also carry the water onto driveways or streets and waste considerable amounts of water. Watering the lawn in the evening or at night may increase disease problems.
Hot, dry summer weather does stress cool season turfgrasses. Proper care of the lawn during this period helps to maintain a healthy, good quality turf.
This article originally appeared in the June 9, 1995 issue, p. 82.