Asked June 06, 2019, 1:47 PM EDT
Hennepin County Minnesota
Thatch is a tightly interwoven layer of living and dead tissue existing between the grass leaves and the soil surface. In highly maintained lawns, organic matter is produced faster than it can decompose. Thatch gradually develops over time. More than 1/2 inch of thatch is a problem in highly maintained Minnesota lawn. More than ½ inch of thatch harbors disease organisms and insects making the lawn more susceptible to damage from disease and drought. Acidic soil, poor soil aeration and waterlogged soils limit the ability of microorganism to breakdown soil. Insecticides and/ or fungicides restrict microorganism and or earthworm activity so thatch builds up faster. Applying excessive amounts of nitrogen, especially in spring, causes thatch to build faster. Fall fertilization in September is better than spring fertilization because the resulting growth is not as rapid and lush. Hollow core aerification promotes better moisture and air penetration into compacted soils. It helps establish a deeper and healthier root system and also stimulates the microbial activity involved in decomposing the thatch layer. The best time to aerate is between late August and early October, depending on how far north you live. Mow your lawn regularly so that no more than one-third of the leaf height is removed with each mowing. Aeration is usually more of a problem with clay soil.