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 pakku (CC BY 3.0) — via Wikimedia Commons
Around 10,000 cherry trees of some 250 kinds around Matsumae Castle, Hokkaido's only Japanese-style castle. Early, mid and late-flowering kinds bloom one after another, about 80% of them double-flowered, so the season lasts about a month. The Matsumae Cherry Blossom Festival runs from late April into May.