TORONTO — For those who like to upend holiday traditions, this trend is for you: the upside down Christmas tree. This season, social media is rife with photos of inverted pines and firs that are adorning hotel lobbies, shopping centres and downtown atriums with gravity-defying drama. It’s a surefire showstopper for retailers eager to attract shoppers, but the over-the-top stunt is now making its way into some living rooms, with several retailers offering up kits for the home decorator willing to try something different. But these trendy inverted trees aren’t cheap.