Viola pubescens Aiton

Common names:

Downy Yellow Violet, Hairy Yellow Violet

Synonyms:

Viola pubescens Aiton, Hort. kew., ed. 1, 3: 290. 1789; Crocion pubescens (Aiton) Nieuwl. & Kaczm., Amer. Midl. Naturalist 3: 215. 1914; Viola uniflora L. var. pubescens (Aiton) Regel, Bull. Soc. Imp. Naturalistes Moscou 34(2): 500. 1861. TYPE: "Nat. of North America. Introd. 1772, by Mr. William Young." Type: Hort. Kew. 1775 (holotype: BM000617590, JSTOR Global Plants image!). [No type was cited, but Taxonomic Literature II states Young's herbarium was deposited at BM. The protologue description suggests a single collection, and thus far only one sheet has been identified. The BM sheet is tentatively accepted as a holotype.]
Viola pubescens Aiton f. peckii (House) Levesque, Naturaliste Canad. 93: 515. 1966; em>Viola pubescens Aiton var. peckii House, Bull. New York State Mus. Nat. Hist. 243-244: 50. 1923; Viola pubescens Aiton var. typica Grover, Ohio J. Sci. 39: 146. 1939 [nomen invalidum]
Viola pubescens Aiton f. eriocarpa (Nutt.) Farw., Pap. Michigan Acad. Sci. 2: 33. 1923 ["1922"]; Viola pubescens Aiton var. eriocarpon Nutt., Gen. N. Amer. Pl.: 150. 1818
Viola pensylvanica Michx., Fl. bor.-amer., ed. 1, 2: 149. 1803

Description:

Caulescent perennials from thick rhizome, stems erect, commonly solitary, ≤ 37 cm tall; stems, foliage and peduncles gray-green to green, lower surface of leaf blades often paler, densely hirsute; leaves cauline (rarely 1 basal leaf), clustered in upper 1/4 of stem; stipules free, broadly ovate, entire or weakly erose; leaves spreading, leaf blades undivided, largest ≤ 75 × 80 mm, upper broadly ovate to reniform, lower broadly reniform, base broadly cuneate to rounded or subcordate, margins serrate, ciliate, apex broadly obtuse to rounded; chasmogamous flower ≤ 13 mm; calyx glabrous or hirtellous, eciliate or ciliate; lowest sepals linear-lanceolate to lanceolate (rarely ovate-lanceolate), acute to obtuse; auricles short and entire, not elongating in fruit; corolla wholly yellow with purple-black lines at base of petals and purple-tinged on back of petals; spur short-globose; lateral petals densely bearded with slightly clavate hairs, spurred petal glabrous; cleistogamous flowers produced after chasmogamous; capsule 7–14 mm, green drying tan or brown, unspotted, glabrous or densely tomentose; seeds 2.3–3.0 × 1.3–1.9 mm, medium orange-brown, unspotted; 2n=12.

Similar species:

This species is very uniform in morphology, as compared to the much more variable V. eriocarpa with which it is often confused. Its typically solitary erect stem, common absence of basal leaves, densely hirsute foliage and peduncle, and undivided broadly ovate to reniform cauline leaf blades clustered near the apex of the stem render it unmistakable. While it differs in several features of growth form, foliage indument, and stipule and leaf features from most populations of V. eriocarpa, occasional populations or individual plants of the latter appear to converge toward this in some features. Consultation of the key will clarify identity of these unusual plants.

Ecology:

Sandy or gravelly soils of dry to dry-mesic forests, drier forested borders of swamps, and well drained slopes in woodlands.

Distribution:

Widespread in e. North America but mostly absent from Gulf Coast states, QC to ND and WY, south to n. SC and e. TX.

Rarity:

State listed in IN; and RI [as V. pubescens var. pubescens].

Phenology:

Chasmogamous flower March–June, chasmogamous fruit April–August, cleistogamous fruit June–August.

Affinities:

This species belongs to the Yellow Violet lineage, sect. Chamaemelanium Ging., in the Nudicaules species group.

Hybrids:

There are many reports of "extensive" hybridization with V. eriocarpa, the erroneously inferred "intergradation" often being used as ammunition to merge the two taxa (Russell 1965, Scoggan 1978). However, there is no empirical evidence thus far to confirm hybridization. In fact, confirmed hybrids in the broader lineage, sect. Chamaemelanium, that contains this and other caulescent yellow-flowered violets are exceedingly rare, and aside from a couple of widely scattered reports of the hybrid of V. canadensis and V. eriocarpa, hybrids are confined to western North America.

Comments:

Brainerd (1921b), Brainerd Baird (1942), Fernald (1950), Henry (1953a), Alexander (1963), Scoggan (1978), Strausbaugh and Core (1978), Swink and Wilhelm (1979), and Weakley et al. (2012) recognized this as a distinct species separate from V. eriocarpa Schwein. (which is sometimes referred to by the misapplied name V. pensylvanica Michx., noted by Jones [1959] as a synonym of the present species). Fernald, Henry, Alexander, and Scoggan additionally recognized var. peckii House for plants with darker foliage and glabrous capsules, but such plants were later found to be distributed throughout the range of the species and are treated here as a population-level polymorphism of fruit indument, and unworthy of formal taxonomic recognition. Russell (1965), Ballard (1995, 2000), McKinney and Russell (2002), Haines et al. (2011), and Little and McKinney (2015) merged V. eriocarpa and the present species, treating them as varieties under V. pubescens, while Gleason and Cronquist (1991), Voss and Reznicek (2012), and Ballard (2013) synonymized all under V. pubescens without formal recognition of infraspecific taxa. Lévesque and Dansereau (1966) conducted thorough studies of the caulescent yellow-flowered violets of the Nudicaules group and provided a compelling case for distinguishing the two taxa at species rank. Recent reevaluation of Missouri populations previously treated by Ballard (2013) as V. pubescens in the broad sense have revealed that they are all typical V. eriocarpa. Conversely, Russell (1965) attributed virtually all Missouri specimens to his V. pubescens var. pubescens.