Awn (botany)

In botany, an awn is either a hair- or bristle-like appendage on a larger structure, or in the case of the Asteraceae, a stiff needle-like element of the pappus.

Among grasses with awns are those commonly known as foxtails, which tend to stick to animals passing by the plant.

During a period of increased humidity during the night, the awns of the spikelet become erect and draw together, and in the process push the grain into the soil.

During the course of alternating stages of daytime and nighttime humidity, the awns' pumping movements, which resemble swimming frog kick, drill the spikelet as much as an inch into the soil.

[1] When awns occur in the Geraniaceae, they form the distal (rostral) points of the five carpels, lying parallel in the style above the ovary.

A wild rye ear ( spike ) with awns
Awns on the fruit of an Australian species of grass
Geranium dissectum fruits, one undischarged, two of which have discharged their seed-bearing carpels by flinging out the seed as the awns dry, shrink, and split off elastically
Awns on the carpels of Erodium moschatum that twist as they dry. They might either fling off their seed, or entangle in the coats of animals, or partly bury the seed if they land suitably on soil.