One of the four solar holidays marking the beginning of spring.  The rejoining of the Mother Goddess and her lover-consort-son, who spent the winter months in death; or the Goddess returning to her Maiden aspect (e.g., Persephone returning from the Underworld.)

Alders are tasseled.
Flag iris is already out on the canal.
... I can see the ... crocuses stammering
in pools of rain, plum blossom on the branches...
False Spring, Boland

Sailors, take warning!