long-day

American  

[lawng-dey, long-] / ˈlɔŋˈdeɪ, ˈlɒŋ- /

adjective

Botany.

1. requiring a long photoperiod in order to flower.

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long-day British  

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

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Etymology

Origin of long-day

First recorded in 1915–20

Example Sentences

In the South, where onions are typically sown in the fall and transplanted to harvest in late spring, short-day varieties are the choice; in the Northeast, where bulb formation happens in the summer from spring transplants, long-day varieties are indicated.

From Seattle Times

To a good approximation, Saturday ended the annual long-day season.

From Washington Post

Long-day onions bulb when day length reaches 14 hours or more.

From Seattle Times

If you’re gardening north of 40 degrees North latitude, be sure to choose long-day onions.

From Seattle Times

Long-day cultivars — American summer berries — are, he said, “optimized for mass production,” at the expense of flavor.

From Washington Post