Downy Yellow Violets ~ Viola pubescens
Downy yellow violets are one of my favorite woodland violets. The heart-shaped leaves set off the bright yellow flowers in early spring. Because of its short stature (6-12"), I use this violet on woodland borders, intermixed with Pennsylvania sedge, rue anemone and virginia waterleaf.
The flowers are attractive to pollinators, especially small bees. The lower petal acts as a nice landing platform and the bold black stripes guide the visitors to the nectar. Nectar is secreted from a gland-like spur on the bottom anthers which are shortened and form a ring around the ovary.
Bees with short tongues such as this shiny, blue, small carpenter bee,
Ceratina sp. have a hard time reaching the nectar in the spur. In order to reach the reward, they turn their bodies upside down.
Long-tongued bees like bumble bees stay right side up and push their head into the flower.
Both the right side up and upside down positions cause the style to be pushed upwards. When a right side up bee inserts its head into the flower, the cone formed by the stamens is opened, releasing pollen onto the top of the visitor’s head and thorax.
In the upside down position, insects land on the front petal and turn themselves upside down. The style is pushed upwards and pollen is released on the face and lower abdomen of the visitor. Subsequent visits to other violets transfer pollen to the receptive stigma.
Small sweat bees,
Lasioglossum sp. are also upside down visitors.
They push their head into the flower as far as possible to try and reach the nectar reward.
Other visitors of downy yellow violet include bee flies (
Bombylius sp.), clouded sulphur butterflies (
Colias philodice) and Syrphid flies.
References:
Beattie, A. J. (1974). Floral evolution in Viola.
Annals of the Missouri Botanical Garden, 781-793. Retrieved from: http://www.jstor.org/stable/2395029
