There are actually two places for viewing cherry blossoms in Nørrebro – Den Sorte Plads (The Black Square) and Den Røde Plads (The Red Square). They have two different kinds of cherries planted that blossom during different times.
When I visited, I had my hopes up for Den Sorte Plads (The Black Square), but the blossoms there are still holding out—they probably need another week or two.
Luckily, just across the street at Den Røde Plads (The Red Square), I stumbled upon a few trees already in full bloom 
The contrast with the vibrant, colorful energy of the square—bikes zooming by, people skating, walking, just living—made the moment even better.