Q. Is it too cold to dethatch my Bermudagrass lawn?  Do I have to wait until next year now? What about overseeding; too late also? If I need to wait, then when? A. It is not too late to dethatch in Las Vegas. Dethatching, sometimes called power raking or vertical mowing, is the removal of dead, grassy material that accumulates on the soil surface where grasses are grown. Dethatching machine, power rake or vertical mower             Bermudagrass is a warm season grass and so becomes dormant or turns brown when temperatures get cold. Bermudagrass produces a lot of this thatch or dead grassy material, more than most grasses. If this thatch is not removed regularly the appearance of a lawn will decline.             Years ago it was burned in the fall. In some rural areas it is still permitted.             In place of fire we use machines that pull the thatch from the lawn. This thatchy material is then disposed of. The best time to dethatch is when the Bermudagrass is actively growing in the summer months or just before overseeding. Thatch             Overseeding is planting a new lawn of cool season grass, such as ryegrass, in the fall just as Bermudagrass is becoming dormant. Thatch will interfere with the seeding of a winter lawn in Bermudagrass. Dethatching the Bermudagrass just before overseeding is commonly done for a better looking winter lawn.             Dethatching now won’t affect your Bermuda lawn but you are getting a bit late for the ideal time to overseed. As temperatures get lower, it takes longer for cool season grass seed to germinate. The ideal time is mid-September through mid-October. Later than this can be a little chancy because we don’t know what the weather will do. How thatch accumulates             It is warmer in the city than in the suburbs so overseeding in the city is more successful later in the fall. As you get closer to the desert or higher in elevation overseeding should be done earlier.             If you miss this time for dethatching, the next best time would be June July and August.