What Weakens Grass?

Low Mowing

• Mowing grass too low robs grass of nutrients. Grasses thrive on nutrients created during photosynthesis, which occurs in the grass blades. Grasses cut too low cannot receive adequate amounts of nutrients, which weakens grass. Poor nutrient intake increases a lawn's susceptibility to weed invasion, disease and injury from drought and summer heat. It also decreases root formation and root growing depth, according to the Ohio State University Extension. Keep mower blades sharp. Correct mowing height depends mostly on the grass species. Kentucky bluegrass should be mowed 1 ½- to 2 ½-inches and Bermudagrass one-half to 1 inch. Never remove more than one-third the grass’ height at one mowing, the Ohio State University Extension reports. Long grass clippings that are left on the lawn after mowing can also block sunlight for photosynthesis.

Drought

• Grass must receive enough water. Several factors influence how much grass should be watered, including species requirements, weather conditions, soil type, how much shade the grass receives and how many other plants near it compete for the same moisture. The Colorado State University Extension points out that a healthy ryegrass lawn may need up to 2 ¼-inches of water per week under the harshest summer conditions, while buffalograss remains green for weeks without watering, even during summer's hottest days. Water grass when it starts appearing wilted and apply enough water to moisten the root zone. Approximately three-quarters to 1 inch of water each time is adequate for most soils, although sandy soils need a little less. As with other plants, the best time to water is late evening or early morning.

Shade

• Photosynthesis requires sunlight, and shade reduces the sunlight. Some grass species tolerate shade better than others do. Grasses frequently weakened from shade have thin, narrow blades; blades that are longer and growing more upright; and reduced shoot and root growth. Fewer blades in total may appear. Chances for diseases in shade also increase, because there is less airflow and increased surface moisture. Water in the mornings and provide less water to grass, unless there are a lot of nearby plants competing for moisture. Trees are pruned to decrease shade. Grasses in shady area grow more slowly. Prevent overfertilization by cutting fertilization by 50 percent.

Extreme Heat

• Grass becomes dormant in hot weather, but extended heat uses up the stored energy in plants, weakening grass. If your area receives very high temperatures in summer, plant grasses that tolerate high temperatures well. During the heat of summer, the Ohio State University Extension recommends raising the cutting height of lawns to approximately one-half inch to reduce heat stress by providing more shade to the lower portion of grass blades and to increase the amount of blade area available for photosynthesis. Grass becomes dormant in cold weather, although grass that was unhealthy before winter can die before spring.