Plants of the Eloise Butler Wildflower Garden

Downy Yellow Violet is a native erect perennial forb of the dry woods, growing up to 18 inches high, but usually much shorter, on leafy stems that have soft velvety hair - more so when young.

Leaves are both basal and on the stem. Basal leaves are long stalked, number 1 to several and with a more rounded shape than the stem leaves. Stem leaves are near the top of the stem and usually number 2 to 4. These are broadly heart-shaped to kidney shaped and larger ones may have lobes near the base. Tips are pointed. Both the basal and the stem leaves have margins with rounded teeth and both have heart-shaped bases. The stem leaves have a rather large pair of stipules at the base of the short leaf stalk. The stipules are ovate in shape with entire margins or just a few coarse teeth. The underside of the leaves is hairy and has prominent leaf veins.

The inflorescence is a solitary flower on a long stalk rising from the upper leaf axils.

The flowers of the Violet family are are two types. Those that form an open flower are called "chasmogamous" (open marriage) and those that never open are called "cleistogamous" (closed marriage). Both types are bisexual (perfect) and set seed but at different times.

The chasmogamous flower is 5-parted with a yellow corolla, averaging 3/4 to 1 1/4 inches wide with each petal (less-so on two upper) having brownish-purple veins showing (nectar guides for insects to reach the nectar spur at the back of the flower). The two side petals are bearded. There are 5 stamens with thin short filaments. Each stamen has a dorsal appendage and the five appendages cohere tightly to form a hollow cone around the central section of the single style. The flower stem has soft hairs. The 5 green sepals of the calyx are narrow and pointed. These flowers open and set seed in the Spring from mid-April to May. A certain percentage can self pollinate.

The cleistogamous flowers are not produced until after the tree canopy is leafed out - May to September. They are smaller and appear to be flower buds in the leaf axils. In most violets the cleistogamous flowers produce the abundance of seed, but not in V. pubescens; here the open flowers are twice as productive in seed production.

Seed: Seeds from both types of flower are similar and are in an ovoid 3-part capsule, sometimes hairy, that contains numerous dull white to pale brown ellipsoid shaped seeds, each 1.8 - 3 mm long, which are ejected when the capsule matures. Viola seeds usually require 60 days of cold stratification plus light for germination.

For details on the flower and seed development see:
(1) Culley T.M. (2002) Reproductive biology and delayed selfing in Viola pubescens (Violaceae), an understory herb with chasmogamous and cleistogamous flowers. International Journal of Plant Sciences, 163, 113-122. (2) Yunjing Wang (2008). Molecular biology of flower development in Viola pubescens, a species with the chasmogamous - cleistogamous mixed breeding system, College of Arts and Sciences of Ohio University.

Varieties: There are two in North America: var. pubescens where the stems and the surfaces of the basal leaves usually have downy hair, and there are only 1 or 2 stems; var. scabriuscula where the stem may be smooth or with downy hair, the basal leaves may be smooth or with sparse rough hair and there are usually 3+ stems. Both are found in Minnesota.

 

Habitat: Downy Yellow Violet is found in rich open woods, mesic to dry conditions. It grows from small rhizomes which can offset and form colonies but it does not produce stolons.

Names: The genus Viola is the very old Latin word for sweet scented flowers. The species pubescens is used when there is soft (or downy) hair on a plant. The author name for the plant classification - ‘Aiton’ is for William Aiton (1731-1793), Scottish botanist, who succeeded Philip Miller as superintendent of the Chelsea Physic Garden and then became director of Kew Gardens, where he published Hortus Kewensis, the Garden’s catalogue of plants.

Comparisons: This violet, like the Canada Violet, has an erect leafy stem from which the flower stem rises, unlike the Common Blue Violet which has basal leaves only and the flower springing from an underground stem. Canada Violet however has white petals.