Sitting on a blue tarp under the trees is THE way to enjoy this season. Of course drinking too much is how it is celebrated as well. When I lived there the park close to my home was Arisugawakoen and had many lovely trees filled with blossoms. Some doubled on a stems.
One of my favorite memories is a year we took our bikes and went to Aoyama Cemetery. There were more old growth trees there and it was so neat to walk among the grave stones. The odd part though and uniquely Japan, was the blue tarps and partying going on. They also sell lots of "carnival" food at these spots. It is because people are there for h-o-u-r-s and get hungry. They sell grilled meats, takoyaki (a personal favorite) and lots of noodles.
When the winds pick up at the end of the season - bringing the rains before the humidity starts to kill you for the summer - it looks like pick snow on the ground.