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 444 spots.

Photo Man On Mission (CC BY-SA 3.0) — via Wikimedia Commons
Hydrangeas cover the slopes of this private garden in Izumi, in the hills inland from Motobu. It opens for the season in early May, the flowers are usually at their best from late May and last until the end of June, and weekdays are quieter than the crowded weekends. Adults 500 yen.