Foxgloves (Digitalis purpurea) are garden plants known for their tall, bell-shaped flowers that create a striking vertical presence. They play a significant role in attracting beneficial insects. This article examines the main insects involved in foxglove pollination and the floral adaptations that support it.
Key Foxglove Pollinators
Bumblebees are the primary and most effective pollinators of foxgloves. Their size and strength allow them to navigate the large, tubular flowers, reaching the deep nectar. Long-tongued species, such as the common carder bee, are particularly well-suited for this task. As a bumblebee forages, its hairy body efficiently collects and transports pollen.
Bumblebees are methodical, often visiting flowers from the bottom of the stem upwards. This behavior aids cross-pollination. Other bee species and hummingbirds may visit, but they are less efficient pollinators.
Foxglove’s Alluring Features
Foxglove flowers have features adapted to attract their primary pollinators. The tubular, bell-shaped corolla acts as a landing platform and guide for larger insects like bumblebees. The lower lip is often extended, providing a stable landing surface. Inside, dark spots or blotches, often edged in white, function as nectar guides, directing the pollinator to the nectar at the tube’s base.
Their downward-facing orientation also guides entry. Fine hairs near the entrance deter smaller insects while offering additional grip. Foxgloves produce abundant nectar, serving as a rich reward that encourages repeated visits from bumblebees.
The Pollination Mechanism
The physical process of pollination involves precise interaction between the pollinator and the flower’s reproductive parts. When a bumblebee enters the tubular flower to access nectar, it brushes against the anthers, which are the pollen-producing structures. Its body becomes covered with pollen as it moves deeper.
Foxgloves exhibit protandry: the male parts (anthers) mature and release pollen before the female part (stigma) becomes receptive. Flowers on a single stalk mature sequentially; older, lower flowers become female while younger, upper flowers are still male. As a bee moves from older, female-phase flowers at the bottom of one plant to younger, male-phase flowers higher up, it collects new pollen. When this pollen-laden bee visits receptive flowers on another foxglove plant, cross-pollination occurs.
Ecological Role and Encouraging Pollinators
Foxgloves contribute to local biodiversity by providing a food source for pollinators, especially bumblebees, during their extended flowering period. Successful pollination produces seeds that disperse easily, allowing the plant to colonize new areas.
Gardeners can encourage pollinators by planting foxgloves in drifts. Providing diverse flowering plants ensures a continuous supply of nectar and pollen. Avoiding pesticides is important, as these chemicals harm pollinator populations. Planting native foxglove varieties is beneficial, as some cultivated forms may produce less nectar.