My favourite cherry blossom spot in Strasbourg is the Citadelle. The remains of the garrison built under Louis XIV are now a gorgeous park by the Rhône-Rhine canal, and the cherry blossoms there are of the variety that bloom into pompoms.
I haven't been to the park this year, only spotting from a distance that the trees are currently in bloom, somewhat earlier than usual. So here are some pictures from a previous year - the year I first saw this wonderful tree at the ruin's entrance.