kingdom Plantae - plants »  divisio Magnoliophyta - flowering plants »  class Rosopsida - eudicots » order Malpighiales »  family Violaceae »  tribus Violeae > genus Viola > Viola sect. Viola  L. > Viola subsect. Rostratae Kupffer    

Viola adunca Sm. - Hookedspur Violet

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Synon.: Lophion aduncum (Smith) Nieuwland & Lunell; V. canina var. adunca (Smith) A. Gray; Viola aduncoides A. Löve & D. Löve; Viola montanensis Rydb.; Viola subvestita Greene

Common name: hook-spur violet , Hookedspur violet, western dog violet , early-blue violet, sand violet   

Description: Plants perennial, caulescent, not stoloniferous, 1.8–30(–35) cm. Stems 1–5, erect, ascending, or decumbent, sometimes later reclining to nearly prostrate, glabrous or puberulent, on caudex from subligneous rhizome. Leavesbasal and cauline; basal: 1–4; stipules linear to linear-lanceolate, margins entire or laciniate with gland-tipped projections, apex acute to acuminate; petiole 0.5–13.5 cm, glabrous or puberulent; blade usually ovate or ovate-deltate to ovate-orbiculate, sometimes ± reniform or oblong, 0.5–6.9 × 0.4–5 cm, base cordate, subcordate, truncate, or attenuate, usually decurrent on petiole, margins crenate to crenulate or entire, ciliate or eciliate, apex acute to obtuse, surfaces glabrous or sparsely to densely puberulent; cauline similar to basal except: stipule margins lacerate to laciniate; petiole 0.5–6.5 cm; blade 0.6–5.5 × 0.4–4.7 cm. Peduncles 1.7–13.8 cm, glabrous or puberulent. Flowers:sepals lanceolate, margins ciliate or eciliate, auricles not enlarged in fruit, 0.5–2 mm; petals light- to deep- to lavender-violet on both surfaces, rarely white, lower 3 usually white basally, dark violet-veined, lateral 2 (and sometimes upper 2) bearded, lowest 7–17(–23) mm, spur purple to violet or white, elongated, 5–7 mm, tip straight or pointed, curved up or lateral; style head sparsely to densely bearded, sometimes beardless; cleistogamous flowers axillary. Capsules short-ovoid, 6–11 mm, glabrous. Seeds dark brown to olive-black, 1.5–2 mm. 

Varieties 2 (2 in the flora): North America.

Viola adunca is polymorphic with over 50 named taxa. G. D. McPherson and J. G. Packer (1974) reported that diploid, triploid, and tetraploid races of V. adunca occur in Canada and northwestern United States. They found that diploid and tetraploid chromosome races can be distinguished morphologically based on style beards and on the size of guard cells and pollen grains and recommended taxonomic recognition of both races. In diploid races, the style projections are more or less cylindrical and about one-sixth the width of the style; in tetraploid races they are short-conical or globular, and about one-tenth or less than the width of the style beard.

Distributional Range: Native Northern America SUBARCTIC AMERICA: Canada, [Northwest Territories, Yukon] Greenland, United States [Alaska] EASTERN CANADA: Canada [Québec, Ontario, New Brunswick, Newfoundland and Labrador] WESTERN CANADA: Canada [Saskatchewan, Alberta, Manitoba, British Columbia] NORTHEASTERN U.S.A.: United States [Maine, Massachusetts, Michigan, New Hampshire, New York, Vermont] NORTH-CENTRAL U.S.A.: United States [Minnesota, North Dakota, South Dakota, Wisconsin] NORTHWESTERN U.S.A.: United States [Colorado, Idaho, Montana, Oregon, Washington, Wyoming] SOUTHWESTERN U.S.A.: United States [California]

Habitat: Mixed forests, forest margins, thickets, grasslands on mountain slopes, moist places and shaded and moist grasslands in stream valleys; 400-2500 m. 

Lower Taxa

• Viola adunca var. adunca

• Viola adunca var. bellidifolia (Greene) H. D. Harrington

Viola adunca var. adunca

Western dog, hooked, early blue, sand, or hookedspur violet, violette à éperon crochu Western dog, hooked, early blue, sand, or hookedspur violet, violette à éperon crochu

Viola adunca subsp. ashtoniae M. S. Baker; V. adunca var. cascadensis (M. S. Baker) C. L. Hitchcock; V. adunca var.kirkii Duran; V. adunca subsp. oxyceras (S. Watson) Piper; V. adunca var. oxyceras (S. Watson) Jepson; V. aduncasubsp. uncinulata (Greene) Applegate; V. adunca var. uncinulata (Greene) C. L. Hitchcock; V. canina Linnaeus var.puberula S. Watson; V. cascadensis M. S. Baker; V. minima M. S. Baker; V. montanensis Rydberg; V. oreocallisGreene; V. oxyceras (S. Watson) Greene; V. sylvestris Lamarck var. puberula E. Sheldon; V. uncinulata Greene

Plants erect, decumbent, or prostrate, (4–)4.5–30(–35) cm. Basal leaves: blade usually ovate or ovate-deltate, sometimes ± reniform or oblong, 1.3–6.9 × 1.2–5 cm, base cordate, subcordate, truncate, or attenuate, apex acute to obtuse, surfaces glabrous or sparsely to densely puberulent, especially abaxially. Cauline leaves: petiole 0.8–6.5 cm; blade 1.1–5.5 × 1–4.7 cm. Peduncles 3–13.8 cm, bracteoles alternate or opposite. Flowers: sepal margins ciliate or eciliate; lowest petal 9–17(–23) mm; style head bearded or beardless. Seeds 1.5–2 mm. 2n = 20, 30, 40.

Flowering Apr–Aug. Dry to moist meadows, open ground, including lawns, damp banks, openings, meadow edges, rocky areas in coniferous or mixed forests, sandy loam; 0–3600 m; Greenland; Alta., B.C., Man., N.B., Nfld. and Labr., N.S., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Iowa, Maine, Mass., Mich., Minn., Mont., Nebr., Nev., N.H., N.Mex., N.Y., N.Dak., Oreg., S.Dak., Utah, Vt., Wash., Wis., Wyo.

Variety adunca can be confused with Viola nephrophylla, which is acaulescent, and with V. labradorica, which lacks decurrent petioles.

H. E. Ballard (1992) noted that eastern specimens of Viola adunca were rarely glabrous, but western ones were often glabrous. Dead, elongated stems often persist on caudices.

J. Clausen (1929) noted that although many American botanists had treated Viola adunca as closely related to or as a variety of V. canina, he thought V. adunca should be treated as a subspecies of the European V. rupestris.

Variety adunca is the food plant for the larvae of the federally listed Behren’s silverspot butterfly (Speyeria zerene behrensii), Myrtle’s silverspot butterfly (S. z. myrtleae), and Oregon silverspot butterfly (S. z. hippolyta).

Evidence of nectar thievery (presence of holes in the spur) has been observed in populations of var. adunca in California and Colorado. Nectar thievery by bumblebees has been reported in Viola hirta and V. riviniana in Europe (A. J. Beattie 1969b).

Viola cascadensis, from Oregon and adjacent Washington, was described by M. S. Baker (1949b) as having dimorphic growth in which, after chasmogamous flowering, the plant changes from acaulescent to caulescent, forming well-developed, nonpersistent stems with cleistogamous flowers, as well as other differences between it and V. adunca.Viola cascadensis was treated as a variety of V. adunca by C. L. Hitchcock et al. (1955–1969, vol. 3) and was synonymized with V. adunca by H. E. Ballard (1992). Study is needed to determine if recognition of V. cascadensis is warranted.

Viola adunca var. bellidifolia (Greene) H. D. Harrington

Violette à feuilles de pâquerette Violette à feuilles de pâquerette

Viola bellidifolia Greene, Pittonia 4: 292. 1901

Plants erect, usually appearing small and tufted, 1.8–4.5(–6.5) cm. Basal leaves: blade ovate to ovate-orbiculate, 0.5–1.7 × 0.4–1.4 cm, base subcordate, truncate, or attenuate, apex usually obtuse, surfaces usually glabrous.Cauline leaves: petiole 0.5–3.8 cm; blade 0.6–1.5 × 0.4–1.4 cm. Peduncles 1.7–5 cm, bracteoles usually opposite.Flowers: sepal margins usually eciliate; lowest petal 7–13(–14) mm; style head sparsely bearded. Seeds 1.5 mm. 2n= 20.

Flowering May–Jul. Alpine areas, wet meadows, lake margins; 2500–3800 m; B.C.; Colo., Mont., Wyo.

Variety bellidifolia is found in the Rocky Mountains. Although forms transitional with var. adunca occur, the diminutive var. bellidifolia is quite distinct. V. B. Baird (1942) reported that Viola bellidifolia occurs in the Siskiyou Mountains of California; we have seen no supporting specimens.

References:

1. Krasnoborov, I.M. & Armemov, I.A. (2012). Opredelitel' Rastenii Respublika Altai: 1-640. Novosibirsk: Izd-vo SO RAN.

• Sheremetova, S.A., Ebel, A.L. & Buko, T.E. (2011). Supplement to the flora of Kemerovo region since 2001 till 2010 Turczaninowia 14(1): 65-74.

• Nikitin, V. (2008 publ. 2009). Violets (Viola L., Violaceae) of republic of Tuva Novosti Sistematiki Vysshikh Rastenii 40: 164-183.

• Czerepanov, S. K. 1995. Vascular plants of Russia and adjacent states (the former USSR) Cambridge University Press.

• Tutin, T.G. & al. (eds.) (1968). Flora Europaea 2: 1-469. Cambridge University Press.