Hordeum pusillum, the little barley, is a diploid annual grass native to the United States (except the westernmost parts), which arrived via multiple long-distance dispersals of a southern South American species of Hordeum about one million years ago. Its closest relatives are therefore not the other North American taxa like meadow barley (H. brachyantherum) or foxtail barley (squirreltail grass, H. jubatum), but rather Hordeum species of the pampas of central Argentina and Uruguay. It is less closely related to the Old World domesticated barley, from which it diverged about 12 million years ago.
The tiny seeds are edible, and this plant was part of the Eastern Agricultural Complex of cultivated plants used in Pre-Columbian times by Native Americans. Before being displaced by maize agriculture, little barley may have been domesticated. Today it can be found in grassland, Sonoran desert, at the edges of marshes, as well as ruderal habitats like roadsides.
- "BSBI List 2007". Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-02-25. Retrieved 2014-10-17.
- "Hordeum pusillum". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 20 January 2016.
- Blattner, F. R. (2006). "Multiple Intercontinental Dispersals Shaped the Distribution area of Hordeum (Poaceae)". New Phytologist 169 (3): 603–614. doi:10.1111/j.1469-8137.2005.01610.x. PMID 16411962. Retrieved April 10, 2009.
- National Plant Data Center (2010). "PLANTS Profile: Hordeum pusillum Nutt. – little barley". The PLANTS Database. Baton Rouge, LA: USDA Natural Resources Conservation Service. Retrieved April 3, 2010.
- Hilty, John (January 28, 2010). "Little Barley". Illinois Wildflowers. Urbana, IL: self-published. Retrieved April 3, 2010.
- Pleines, T.; Blattner, F. R. (2008). "Phylogeographic Implications of an AFLP Phylogeny of the American Diploid Hordeum Species (Poaceae: Triticeae)". Taxon 57 (3): 875–881. Retrieved April 10, 2009.[clarification needed]
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