A dethatcher or lawn scarifier is a device that removes

thatch Thatching is the craft of building a roof with dry vegetation such as straw, Phragmites, water reed, Cyperaceae, sedge (''Cladium mariscus''), Juncus, rushes, Calluna, heather, or palm branches, layering the vegetation so as to shed water away fr ...

from

lawn A lawn () is an area of soil-covered land planted with Poaceae, grasses and other durable plants such as clover lawn, clover which are maintained at a short height with a lawn mower (or sometimes grazing animals) and used for aesthetic an ...

s. Types of dethatchers include motorized dethatchers or those that can be pulled behind a garden tractor.

Thatch removal (dethatching)

Scarification or de-thatching of lawns or turf is a mechanical process whereby the surface and subsurface of the lawn, green or sports pitch is rigorously abraded by penetrating metal blades, tines or prongs. The process is usually carried out by machines of a professional standard which are normally powered by gasoline engines. Smaller, less rigorous electric machines are also available for the domestic market. The process of scarifying is designed to remove thatch from lawns. Thatch is a build-up of organic matter which can include dead grass, leaves, stems,

stolon In biology, a stolon ( from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as a runner, is a horizontal connection between parts of an organism. It may be part of the organism, or of its skeleton. Typically, animal ...

rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...

s and overcrowded grass roots and lateral weed growth. Thatch can stifle the growth and health of grass or

turf Sod is the upper layer of turf that is harvested for transplanting. Turf consists of a variable thickness of a soil medium that supports a community of turfgrasses. In British and Australian English, sod is more commonly known as ''turf'', ...

. Removing the thatch helps the grass by encouraging it to thicken up and also makes it stronger and less susceptible to disease. Reducing thatch levels increases the levels of water, air and nutrients that can get through to the root zone of the grass plants. Significant thatch problems in lawns can cause diseases and can encourage moss to grow in the areas where grass has died. A by-product of scarifying or de-thatching is that

moss Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Wilhelm Philippe Schimper, Schimp. 1879) may also refer to the parent group bryo ...

is also removed, and depending on how deep the scarifying blades are set, root cutting can also occur, and this in turn helps grass to thicken up over time. Scarifying is normally carried out in autumn or spring. When scarifying or de-thatching, not all thatch should be removed as a small amount of thatch is beneficial to the lawn. A lawn that has excessive thatch may feel spongy when trodden upon. After removing thatch, it can be swept or raked up using a lawn sweeper.

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{{Garden tools Gardening tools Horticultural techniques Lawn care