Kingdom: Plantae
(unranked): Angiosperms
(unranked): Monocots
(unranked): Commelinids
Order: Poales
Family: Poaceae
Genus: Setaria
Species: S. pumila
Binomial name: Setaria pumila
Common name: Yellow bristle grass, Yellow foxtail, Pigeon grass, Cattail grass. Garden bristle grass, Hairy-tail grass, Yellow bristlegrass, foxtail, Cat's tail grass.
Setaria pumila is a species of a summer active annual, summer growing grass that is native to Europe, but it is known throughout the world as a common weed that is a threat to pastoral farming. It invades cultivated fields, lawns, roadsides, disturbed areas and many other places. In New Zealand, Setaria pumila can cover 20-40% of otherwise productive dairy farming pasture causing a loss in milk production. It does this by competing with ryegrass and other sown pasture species. Setaria pumila forage is of poor quality and dairy cattle avoid grazing plants with mature seeds, which can reduce the available forage. In 2016 it was estimated Setaria pumila was costing New Zealand dairy farmers between $350-$1100/ha depending on the level of infestation.
This extremely aggressive grass grows 20 centimetres to well over a meter in height, its mostly hairless stems range from green to purple-tinged in colour. The leaf blades are hairless on the upper surfaces, twisting, and >170 mm long, 5-9 mm wide.
The inflorescence is a stiff, cylindrical bundle of spikelets 2 to 15 centimetres long with short, blunt bristles. The panicle may appear yellow or yellow-tinged. A plant can produce seeds within 4 to 8 weeks of emergence if conditions are favourable. Mature plants can produce seeds heads that can contain 100s of seeds between grazing (Tozer & Cameron). The barbed seeds are spread by adhering to animal hair, feathers and clothing. Its seeds pass through the cow's rumen and are spread around farms in their dung.
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The seed heads.
A spikelet
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Thanks to Wikipedia for text and information https://creativecommons.org/licenses/by-sa/3.0/
