long-day

[lawng-dey, long-]

adjective

Botany.

1. requiring a long photoperiod in order to flower.

long-day

adjective

1. (of certain plants) able to mature and flower only if exposed to long periods of daylight (more than 12 hours), each followed by a shorter period of darkness Compare short-day

Word History and Origins

Origin of long-day¹

First recorded in 1915–20