Viola retusa E.L. Greene. Section: Nosphinium. Subsection: Borealiamericanae. Common name: Great Plains Violet. Phenology: Chasmogamous flower Apr-May; chasmogamous fruit Apr-Jul; cleistogamous fruit May-Oct. Habitat: Gravel riverbanks along rivers and streams, sometimes under open woods bordering riverbanks, in the Great Plains. Distribution: N. ND to n. WY, south to e. KS, c. TX and nc. CO.

ID notes: This species is most similar to other Borealiamericanae violets with leaves longer than broad in chasmogamous flower that broaden to as broad as long in fruit, namely V. affinis, V. cucullata, V. species 3, V. langloisii, and V. missouriensis; it has also been confused with V. nephrophylla, which is regionally sympatric with this species and occasionally grows near it. In chasmogamous flower it differs from all of the above in the slender commonly retuse upper petals, from V. cucullata, V. species 3, V. langloisii, and V. missouriensis in its densely bearded spurred petal, additionally from V. cucullata by its lateral petal beards with long filiform hairs and from V. missouriensis in its narrower long-acuminate eciliate sepals; from V. affinis in its glabrous foliage and peduncle, and prominent auricles. In cleistogamous fruit it can be distinguished from V. affinis and V. missouriensis by its unspotted cleistogamous capsule on an eventually erect peduncle, and medium brown spotted seeds; from V. cucullata and V. species 3 by its shorter auricles and spotted seeds; from V. langloisii by its erect leaves, erect cleistogamous peduncle, and medium brown spotted seeds; from V. nephrophylla but its glabrous foliage, leaf blades with abruptly acute to acuminate apex, slender long-acuminate sepals, prominent auricles, and larger spotted seeds.

Origin/Endemic status: Native

Taxonomy Comments: Mysteriously showing up in Brainerd’s treatment of violets in the 1913 Britton and Brown illustrated flora, but not in his 1921 summary of North American violets. Recent studies have nevertheless shown it to be distinct from V. nephrophylla and other species in several traits; it appears to rarely occupy the same sites as V. nephrophylla. It has been virtually ignored as a Great Plains endemic, and is surely more common than the sporadic herbarium collections suggest. While not yet confirmed in the region, it occurs within a couple of counties of sw. MO, and its future discovery is expected.

Synonymy ⓘ: = K4, POWO, Ballard, Kartesz, & Nishino (2023); < Viola nephrophylla Greene — FNA6, NS. Basionym: Viola retusa Greene 1899

Links to other floras: < Viola nephrophylla - FNA6

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Wetland Indicator Status:

• Eastern Mountains and Piedmont: FACW (taxonomic split from wetland indicator species)
• Great Plains: FACW (taxonomic split from wetland indicator species)
• Midwest: FACW (taxonomic split from wetland indicator species)
• Northcentral & Northeast: FACW (taxonomic split from wetland indicator species)

Heliophily ⓘ: 5