Mandan ricegrass

×Eriosella caduca (Beal) Romasch.

Mandan ricegrass carries a botanical meeting in its name. The multiplication sign marks a hybrid associated with Indian ricegrass, Eriocoma hymenoides, and green needlegrass, Nassella viridula. The two parents belong to different grass genera, reflected in the combined generic name ×Eriosella. Earlier accounts used the name ×Achnella for this same cross. Kew Plants of the World Online: ×Eriosella caduca Peterson et al. 2019, PhytoKeys 126: A key to the North American genera of Stipeae

Botanical name

The database name ×Achnella caduca is an explicit homotypic synonym of Kew’s accepted ×Eriosella caduca. The 2019 combination cites the same Montana type, US-745838; identity is unchanged. Kew Plants of the World Online: ×Eriosella caduca Peterson et al. 2019, PhytoKeys 126: A key to the North American genera of Stipeae

Recognizing the plant

This perennial grass grows in tufts, with narrow blades and stems described as reaching about ninety centimeters. Its flower cluster is a narrow panicle with upward-pointing branches. Small hairy florets carry awns that detach readily, a useful detail for separating the hybrid from similar grasses. The narrow blades, compact flowering array and hairy florets bring its diagnostic details together on the same stem. Peterson et al. 2019, PhytoKeys 126: A key to the North American genera of Stipeae

Native range

The hybrid is documented in northern North America. The 2019 taxonomic account records Montana, North Dakota and western Wyoming, while Kew’s distribution also extends into Canada. The original specimen behind its name was collected in Montana, providing a geographic anchor for the later botanical combinations. Kew Plants of the World Online: ×Eriosella caduca Peterson et al. 2019, PhytoKeys 126: A key to the North American genera of Stipeae

Botanical sources

Reviewed 2026-10-11. Seasonal development varies with location and growing conditions.