USA NPN National Phenology Network

Taking the Pulse of Our Planet

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An observable stage or phase in the annual life cycle of a plant or animal that can be defined by a start and end point. Phenophases generally have a duration of a few days or weeks. Examples include the period over which newly emerging leaves are visible, or the period over which open flowers are present on a plant. (See also phenological event) (Note: The definition of the term “phenophase” has not yet been standardized and varies among scientists. The definition presented here reflects our usage of the term on the USA-NPN website.)

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