Definition of short-day in US English:

short-day

adjective

  • attributive (of a plant) needing a daily period of darkness of more than a certain length to initiate flowering, which therefore happens naturally as the days shorten in the autumn.

    • ‘Flowering requires or is accelerated by short photoperiods in the so-called short-day plants, while the opposite is true for long-day plants.’
    • ‘For example, short-day onions grow in southernmost climes.’
    • ‘The effects of the mutation are often more obvious under unfavorable conditions, ie. short photoperiods for long-day plants and long photoperiods for short-day plants.’
    • ‘The two main photoperiodic response categories are short-day plants and long-day plants, in which flowering occurs in short or long days, respectively.’

Pronunciation

short-day

/ˈSHôrtdā/