Flipping Christmas upside down has been a pretty hot retail trend in recent years. Turns out, it was a pretty hot trend nearly a thousand years ago, too.When Grant Whitney, the owner of the new Studio V hair salon in Felida, was getting ready to launch his business in May, his interior designer sized up the place’s high ceiling and offered a fun idea: When the holiday season approaches, why not dangle an inverted Christmas tree up there?Whitney’s reaction: A what? “I guess that’s a thing. I’d never seen one,” he said.He quickly learned that upside-down Christmas trees have been growing in popularity since the turn of the century — especially in stores and showrooms where sales space is at a premium. A wide-shouldered tree that’s balanced on one little toe doesn’t just grab the eye and tickle the curiosity, it also leaves more square footage open on the floor.All sorts of upside-down trees are available via all sorts of sellers. Wal-Mart’s most affordable, an unadorned 3-foot artificial “tear drop,” goes for $35 and you can dangle it over a door; the Hammacher Schlemmer clearinghouse of conspicuous consumption offers a 7-foot upside-down tree featuring “3,700 lifelike PVC branch tips that are carefully pre-strung with 800 bright clear commercial-grade lights.” It goes for $600. The $65 base is extra.The small tree Whitney settled on is supposed to stand in a base, but he had a better idea: He lopped off the base attachment and hot-glued a big light to the point at the top — that is, the bottom. And he affixed the tree to an exposed pipe up near the ceiling of the back room where you go to get shampooed.