12. Viola pubescens Aiton (yellow violet, smooth yellow violet)

V. pubescens var. eriocarpa (Schwein.) N. Russell, an illegitimate name

V. pubescens var. scabriuscula Torr. & A. Gray

V. eriocarpa Schwein.

V. eriocarpa var. leiocarpa Fernald & Wiegand

V. pensylvanica Michx.

V. pensylvanica var. leiocarpa (Fernald & Wiegand) Fernald

Pl. 576 f, g; Map 2703

Plants perennial, with a stout, prostrate to ascending rhizome 3–5 mm thick. Stems 10–35 cm long, erect or ascending, sometimes from a spreading base. Leaves alternate (some nodes sometimes appearing subopposite) and sometimes also basal at flowering, short- to long-petiolate, the petiole glabrous or hairy. Stipules relatively small and inconspicuous, free from the petiole, unlobed, the margins entire or shallowly and irregularly toothed. Leaf blades 1.5–7.0 cm long, unlobed, ovate to heart-shaped or somewhat kidney-shaped, angled (often broadly so) or broadly rounded at the tip, rounded to cordate at the base, the margins evenly and bluntly toothed, the surfaces glabrous or hairy. Cleistogamous flowers produced. Flower stalks not or only slightly overtopping the leaves (those of the cleistogamous flowers erect or ascending). Sepals 3–6 mm long, lanceolate, angled to a sharply pointed tip, the margins sometimes minutely hairy, the basal auricles short and inconspicuous. Corollas 8–12 mm long (except in cleistogamous flowers), the petals oriented forward with arched or outward-curved apical portions, longer than the sepals, yellow, the upper and lateral petals sometimes brownish-tinged on the undersurface, the lateral and especially the lower petals usually with dark purple to brownish purple veins, the lateral petals bearded on the upper surface with mostly knob-shaped hairs, the lowermost petal glabrous on the upper surface, the spur minute (the lower petal often appearing merely pouched), not or only slightly exserted beyond the sepal auricles, relatively stout. Stamens not exserted, typically not visible without dissection of the flower. Style club-shaped, with a capitate, bearded tip. Fruits 9–12 mm long, narrowly ellipsoid to ellipsoid, green, drying to tan to olive-colored, the surface glabrous or densely woolly. Seeds 2.1–2.4 mm long, brown. 2n=12. March–May.

Scattered to common throughout the state (eastern U.S. west to North Dakota, Wyoming, and Texas; Canada). Bottomland forests, mesic upland forests, bases and ledges of bluffs, banks of streams and rivers, and margins of sinkhole ponds; also edges of pastures and shaded roadsides.

This species is represented over much of eastern North America by two morphological and ecological extremes treated by many botanists as varieties (Steyermark, 1963; Ballard, 1994). Plants of var. pubescens tend to produce a single, erect or strongly ascending aerial stem, 1 or no basal leaves at flowering, relatively densely hairy foliage, ovate to somewhat kidney-shaped leaf blades with broadly angled to truncate bases, and herbaceous, ovate upper stipules, whereas plants of var. scabriuscula usually produce several aerial stems that are ascending from spreading bases, several basal leaves at flowering, glabrous to sparsely hairy leaf blades, heart-shaped to broadly ovate leaf blades with usually cordate bases, and semi-herbaceous lanceolate upper stipules. Unfortunately, a substantial proportion of collections across the range of the species defy confident assignment to either variety; indeed, the vast majority of Missouri specimens are at least partially referable to var. scabriuscula, but few specimens match the extreme morphologies of either variety. Neither variety is accepted here, given the difficulty of interpreting Missouri material.