dandelion clock

dandelion clock (plural dandelion clocks)

1. A single stem of a dandelion in its post-flowering state with the downy covering of its head intact. The term is applied when the flower is used, or is thought of as suitable for use, in a children's pastime by which the number of puffs needed to blow the filamentous achenes from a dandelion is supposed to tell the time.
   • 1841 April 1, “Breakfast Table Science for Young People”, in Parley's Magazine‎, New York, page 112:

     Dandelion clocks! -- Pray what are they? ... by far the best clock is made by blowing the downy seed of the dandelion.

• “dandelion clock” (US) / “dandelion clock” (UK) in Oxford Dictionaries, Oxford University Press.