dethatch

Dethatching is the lawn care practice of removing the thatch layer—the layer of dead and living plant material that accumulates between the soil surface and green grass growth. Thatch consists of dead leaves, stems, and roots. A thin thatch layer can protect the soil, but when it thickens it blocks water, air, and nutrients from reaching the soil and can create a habitat for disease and pests. A typical lawn benefits from keeping thatch to about one-half inch (12 mm) or less.

It is most effective when the lawn is actively growing. Cool-season grasses are best dethatched in early spring or early fall; warm-season grasses in late spring to early summer. Avoid dethatching during drought, extreme heat, or when the lawn is stressed.

Dethatching can be done with a manual rake or with a specialized dethatching machine. Manual dethatching uses a rigid rake or thatching rake to pull out the thatch. A powered dethatcher or vertical mower cuts into the layer with tines or blades and lifts it from the lawn. Aerators and core aeration are separate practices that relieve soil compaction and are sometimes performed in the same season.

After dethatching, remove debris, water to help recovery, and consider overseeding bare spots. Fertilize according to soil test and follow up with proper irrigation. Do not dethatch newly seeded lawns, and avoid aggressive dethatching on weak or drought-stressed turf. If thatch is still excessive after one pass, re-treat at the recommended interval or consult a professional.