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 t-konno (CC BY-SA 3.0) — via Wikimedia Commons
A lavender field on a university campus in Sapporo, opened to the public in July. The Minamisawa Lavender Festival is held there, with a brass band concert and stalls; free.