Q: Why do you recommend keeping the grass at least 3 inches tall and cutting with a sharp blade?
A: Cutting your grass short during the heat of summer or cutting with a dull blade any time of year will damage and wither the grass. This also invites weeds, especially crabgrass. In the summer, research shows that dense fescue-type grass, like Pearl's Premium, grown to at least 3+ inches tall will shade the soil and prevent most weed seeds from germinating. Without any chemical herbicides, 4-inch tall Pearl’s Premium type grass can limit weed concentrations to 2-5% (much lower than popular bluegrass). Less dense 4-inch tall bluegrass lets more light in and has 7+ % weeds. However, short 1 inch bluegrass lets in so much light, it can have 55% to 75% weeds and one inch short fescue type grass has 45% weeds because it lets more light reach the weed seeds sitting on top of the soil. Cutting your grass too short will encourage shallow roots, making it hard to tap into naturally-occuring moisture and nutrients in your soil. Equally bad, using a dull lawn mower blade will damage your grass, tearing the blades, opening pathways for disease and extending the time to heel. A dull blade and cut too short is a guaranteed way to burn out and kill the grass during extreme heat. Ideally, keep your grass 3+ inches tall for most of the season. In extreme heat, consider leaving your lawn 4 inches tall for maximum resistance. In the fall, consider cutting to 2 inches high, as no new weeds come up at that time, to faciliate fall clean-up. To keep grass strong, do not cut back more than 1/3 of the blade at a time, and use a sharp blade so the grass cut edge seals up quickly and does not allow disease or fungal infections to get in.