late bloomer; flower blooming out of season
Poetic term for a flower that blooms after its usual season, especially in winter. Often carries a wistful or lonely nuance.
庭に忘れ花が一輪、寒そうに咲いていた。
A single late bloomer was blooming in the garden, looking cold.
冬の忘れ花は、どこか寂しげな風情がある。
Winter's out-of-season flowers have a somewhat lonely elegance.
Compound of 忘れ (wasure, 'forgetting') + 花 (hana, 'flower'). The exact origin is uncertain, but it likely refers to a flower that seems to have 'forgotten' to bloom in its proper season.