Photoperiod
/FOH-toh-PEER-ee-ud/🦋 Ecology●● Intermediate
Also known as: day length, daylength
The number of hours of light and darkness in a day, which triggers physiological responses in plants including flowering, dormancy, tuber formation, and leaf senescence. Short-day plants (chrysanthemums, poinsettias) flower when nights are long; long-day plants (lettuce, spinach) flower when days are long; day-neutral plants are unaffected.
Etymology
Greek photos (light) + periodos (circuit, period of time)
Example
“Poinsettias are short-day plants that require 14 hours of darkness daily for 6 weeks to initiate flowering.”