It's interesting to see the cold response that different grasses exhibit this time of year. Cool season turfgrasses like bentgrass and bluegrass also enter a phase of dormancy but not to the extent of warm season grasses like Bermudgrass. All of the new Kentucky Bluegrass (KBG) sod that was laid during last winter's project, really turned brown- more so than other KBG varieties on the golf course. There really is n explanation for this other than genetics. It isn't a bad thing either as it will green up next spring without any trouble.