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Riverbank Wildrye (Elymus riparius Wiegand)

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Summary
Range
Similar Plants
Habitat
Life Cycle
Fauna
Uses
Relatives
Notes
Links
Photos

Photo © Henry Frye, Public Domain.

↑Summary

A perennial, cool-season bunchgrass native mostly to northeastern North America, typically found in riparian areas.

↑Range - Expand

Legend	Color
Native
Native or Not Present
Introduced or Not Present

This tentative map is based on our own research. It may have limited data on Canada and/or Mexico, and there is some subjectivity in our assignment of plants as introduced vs. expanded. Read more in this blog post.

Although this plant occurs somewhere in each of these regions, it may only occur in a small part of some or all of them.

↑Similar Plants

Canada Wildrye (Elymus canadensis)
View - Compare

Early Wildrye (Elymus macgregorii)
View - Compare

Silky Wild Rye (Elymus villosus)
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↑Habitat

Found primarily in riparian areas, including floodplain forests, clearings, and grasslands such as meadows and prairies, usually along larger streams, where it grows right up to the water's edge, and sometimes ventures farther from the stream in broad, flat floodplains and swamps adjacent to streams or rivers. Occasionally found in ditches and wet depressions in upland areas, and in sheltered coves in rich montane forests in the Appalachians.

Usually found in moist conditions, but ranges into mesic conditions in shade. Most often found in partial to light shade, with an open canopy letting through some light, but also ranges into full sun on moist sites. Tolerates a range of soil textures including clay-loam, loam, silt, and sand, and even some soils with rocky or gravely material, but seems to prefer alluvial soils, which tend to be porous and nutrient-rich.

Common and abundant in the portion of its range from northeast Ohio through Pennsylvania and New York State into southern New England, but becomes more scattered to uncommon in the Midwest and scattered and rare in the southeastern coastal plain.

Compared to other native Elymus species, this one prefers the wettest conditions, but is the least drought-tolerant. Its shade tolerance is intermediate, considerably less than eastern bottlebrush grass (Elymus hystrix) but more than canada wildrye (Elymus canadensis). It often occurs together with Virginia wildrye (Elymus virginicus).

↑Life Cycle

This species is a cool-season perennial bunchgrass that flowers later in the season than most other members of its genus.

We found some sources saying that this species is short-lived, but we have also observed individual plants living over 7 years. We have not found any reliable sources establishing its lifespan.

↑Faunal Associations

We unfortunately could not find any information on relationships between this species specifically. Native Elymus species however tend to support a large number of insect herbivores.

↑Uses

This species is occasionally used for erosion control within its range, and is excellent for this purpose. It is often mixed with Virginia wildrye (Elymus virginicus), which ranges into more mesic moisture conditions.

The exact taxonomic relationships in Elymus are poorly understood and it is not known which species in this genus this one is closest related to.

Riverbank wildrye is more reproductively isolated from other members of the Elymus genus than most are with each other. It has been recorded hybridizing with Virginia wildrye (Elymus virginicus) var. virginicus, and with eastern bottlebrush grass (Elymus hystrix), but the hybrids are usually sterile, often not even producing any seed spikes.

↑Notes

This is one of the many species negatively affected by the invasive plant lesser celandine (Ranunculus ficaria), which tends to dominate in the riparian habitats where this plant grows. Because that plant emerges earlier and this species does not form a long-term seed bank, the competition tends to inhibit seed germination, and often the seeds end up perishing because the competing foliage persists past the time window optimal for this species to germinate and establish. Removal of lesser celandine tends to benefit this species.