Cherry blossom is three weeks of it. Flip through the other forty-nine — and watch what's in bloom move up and down the country.
The calendar is the way in. Underneath it sits the ordinary thing — search, filter by month or flower, and open any of the 412 spots.

Photo PlusMinus (CC BY-SA 3.0) — via Wikimedia Commons
About 200 plum trees in the grove inside the old imperial park, including Omoi-no-mama, which carries red and white flowers on the same tree. Free and open all day.