October at Jamaica Pond turns the water to pewter and the maples to something louder, and the lawns around it begin their long slide toward dormancy. Christie Dustman & Company, Inc. tends Boston turf through that turn — final mows held at the right height, leaves pulled off the crown before they mat, bed lines cut so they survive until spring. Autumn is when the next season is actually decided: overseeding, feeding, cutting back. It is unhurried work, done in cold air, with the light going gold by four o'clock. Come April the difference shows without anyone having to explain why.