Description: This native perennial plant consists of a small rosette of basal leaves (usually 3 or more), from which one or more stems up to 1' long may develop. These stems are hairless, finely pubescent, or somewhat hairy. The blade of each basal leaf is up to 3" long and 2½" across; at its base, there is a stout petiole up to 3" long. The petioles can be hairless or hairy. The basal leaves are orbicular-cordate or oval-cordate, crenate-dentate along the margins, and palmately veined. For var. eriocarpa of this species, each margin of a leaf (whether left or right) has a total of 16-18 teeth. This variety of Viola pubescens has less hairy leaves than the typical variety; the upper surface of each leaf is usually hairless, while the lower surface may have a few hairs along the major veins. The cauline leaves alternate along the stems; they are similar to the basal leaves, but smaller in size. There is a fairly large stipule where the base of a petiole joins the stem; this stipule is lanceolate-ovate.
The flowers develop from the axils of the
cauline leaves; they do not occur on separate stalks from the rootstock. Each
flower is about ¾" across, consisting of 5 rounded yellow petals and 5
light green sepals. The beardless lower petal has prominent purple veins toward
its base. Each of the 2 lateral petals has a beard at its base consisting of a
small tuft of white hairs; sometimes there are a few purple veins outside of
each beard. The 2 upper petals are beardless and they usually lack any darker
veins. Each flower occurs at the apex of an individual stalk that is as long as
the leaves; this stalk nods downward at its apex, causing the flower to face
outward from the stem. The blooming period occurs from mid- to late spring and
lasts about a month. There is no noticeable floral scent. Later, cleistogamous
flowers are produced that lack petals; they can produce fertile seed without
insect pollination. Each fertile flower is replaced by a tripartite cluster of
spreading seed capsules; each seed capsule is elongated and pointed at its tip.
These seed capsules eventually turn brown and split apart; they can eject the
seeds several inches from the mother plant. Each small seed is globoid and
brown. The root system consists of scaly rhizomes, which can form vegetative
offsets. This plant occasionally forms colonies.
Cultivation: The preference is light shade to
partial sun, moist to mesic conditions, and a rich loamy soil with abundant
organic matter. Medium shade is tolerated later in the year after the trees
develop their leaves. The foliage is little bothered by disease.
Range & Habitat: Common Yellow Violet is a
common woodland wildflower that occurs in nearly all areas of central and
northern Illinois; it is slightly less common in southern Illinois. Habitats
include moist to mesic deciduous woodlands, woodland borders, and thickets.
Unlike Viola pratincola (Common Blue Violet), it is not often observed
in yards and other disturbed areas.
Faunal
Associations: The nectar and pollen of the flowers attract primarily
bees, including Little Carpenter bees, Mason bees, Cuckoo bees (Nomadine),
Miner bees (Eucerine), Anthophorine bees, Halictid bees, and Andrenid bees.
Less common insect visitors include Bombylius major (Giant Bee Fly),
small butterflies and skippers, and Syrphid flies. Syrphid flies feed on pollen
and are non-pollinating. The caterpillars of several Fritillary butterflies and
moths feed on the foliage of Violet spp. (Violets). See the
Butterfly & Moth Table for
a listing of individual species. The seeds are eaten in limited amounts by the
Slate-Colored Junco and various upland gamebirds, including the Ruffed Grouse,
Bobwhite, Wild Turkey, and Mourning Dove. Both the Cottontail Rabbit and
White-Tailed Deer have been known to feed on the foliage of Violets, but this
is rather uncommon.
Photographic
Location: A mesic deciduous woodlands at Busey Woods in Urbana,
Illinois.
Comments: The Common
Yellow Violet can be difficult to distinguish from the less common typical
variety, Viola pubescens pubescens (Downy Yellow Violet). The Downy
Yellow Violet is restricted largely to northern Illinois. It differs from
Common Yellow Violet by its hairier leaves (conspicuously pubescent on the
upper surface) and more abundant teeth along the leaf margins (more than 18
teeth per margin, whether left or right). The Downy Yellow Violet usually
produces only 1-2 basal leaves per plant and it is less likely to produce more
than one stem per plant. However, in many areas of Illinois, there is a
tendency for these two varieties to intergrade, producing plants with
intermediate characteristics. For this reason, they are longer considered
separate species by most authorities. This is the only Viola sp.
(Violet) in Illinois with yellow flowers, although there are additional
yellow-flowered species of Violet occurring in areas lying to the east, north,
and west of the state.