What Causes Thatch?
Thatch accumulates when the rate of shoot growth exceeds the rate at which the above ground parts of the plant decompose. Practices which promote excessive shoot growth increase thatch production.
Thatch Control
The best way to determine how much thatch you have is to cut a square from your turf and examine the thatch layer. In Kentucky bluegrass more than 1.25 cm is considered to be too much. In the case of creeping bentgrass anything more that .75 cm can be a problem. If thatch has accumulated beyond that action should be taken to control it. There are various methods for thatch control:
Vertical mowing
Vertical mowing or verticutting is a method of reducing thatch by cutting it up with a blade which runs perpendicular to the ground. Blades should be space about 4.0 cm and set shallowly to just cut through the top most portion of the thatch. Often several passes in several directions are necessary. Verticutting should not be done towards winter time. The other time when verticutting is recommended is in spring. Again turf need 30 days to fill in before the hot summer weather comes. Crowns that are exposed during the heat of the summer are more prone to high temperature stress. Vertical mowing can be followed by a light topdressing to protect the exposed crowns and a light fertilizer application to stimulate regrowth.
