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 Σ64 (CC BY-SA 3.0) — via Wikimedia Commons
Two marsh lakes covered with lotus in summer. During the lotus festival from late July to late August, small boats take you about 25 minutes through the flowers; go in the morning.