Penstemon digitalis, also known as foxglove beardtongue, is a perennial native that typically grows to a height of two to three feet and produces a profusion of white or light pink flowers that bloom in early summer. Like many other flowering plants, Penstemon digitalis relies on pollinators to transfer pollen.
Penstemon digitalis is primarily pollinated by bees, especially solitary bees belonging to the family Megachilidae. These bees are attracted to the flowers of the plant by their sweet nectar and bright coloration. When a bee lands on a flower, it brushes against the anthers, the male reproductive organs of the flower, and picks up pollen on its body. As the bee moves from flower to flower, it transfers the pollen to the stigmas, the female reproductive organs of other flowers. This process, known as cross-pollination, fertilizes the flowers and produces of viable seeds.
Other insects, such as butterflies and moths, also visit Penstemon digitalis flowers, but they are less effective pollinators than bees. Butterflies and moths are attracted to the flowers by their color and scent, but they do not have the specialized body structures that allow bees to efficiently transfer pollen from flower to flower.
Penstemon digitalis has evolved a mechanism to prevent self-pollination, which can reduce the genetic diversity of the plant population. The stamens are positioned above the stigma in such a way that the pollen must be transferred by a pollinator in order to reach the stigma. This arrangement ensures that the plant cannot fertilize itself