What are dethatching and scarifying? Does my lawn need one of them?

Dethatching and scarifying are different processes that remove thatch from a lawn that has built up over time. They removes excess thatch, allowing water and nutrients to penetrate the soil, and encouraging the healthy grass to flourish. Dethatching is more superficial, usually using metal tines or a rake to remove. Scarifying is a deeper and more intense process, usually using blades that penetrate the soil, so it should be timed very strategically to avoid overstressing your grass.

Thatch less than ½-inch thick benefits your lawn, but a thicker thatch layer can harm it. In order to measure your lawn's thatch level, you can use a trowel to dig a small core sample as illustrated here. It's important to only dethatch when needed. Typically, only spreading or creeping grasses need dethatching; bunching grasses do not. Proper timing is crucial for all dethatching projects to ensure the grass is actively growing and can withstand the stress of the procedure. Warm-season grasses are usually dethatched in late spring or early summer (i.e. April-June) while cool-season grasses are usually dethatched in early spring or early fall (i.e. March-May or August-October).