sleep-flower

Noun

sleep flower (plural sleep flowers)

1. (literary, poetic) A poppy, particularly the opium poppy, Papaver somniferum, whose extract was traditionally used as a sleep aid.
   • In the cracks of the marble floors, in the crannies of the walls, springing from beneath the broken statue, voiceless yet persistent, grow scarlet poppies — the sleep flowers of the world, yielding to this yellowing Temple of Mysteries the quieting influence of their presence.1900, Lilian Bell, As Seen By Me
2. Any flower whose consumption, in whole or in part, causes the consumer to fall asleep.
   • After the lazy lover had sown the sleep seed all over the grounds, he went away.[…] All along the galleries it grew and grew, and in a few days the air of the place was heavy with the scent of the pale-coloured sleep-flowers. Then the whole world of the palace began to drowse.[…] And the pale...1875, “The Sleep Seed”, in The Peep-show: for Little Readers, Oxford University