There’s a lot of purple showing in the mid-summer landscape. On a bike ride along our favorite bike trail, we stopped to investigate. What are those beautiful blue to purple flowers growing along the side of the trail? My Picture This app says they are American bell flowers. Once we’ve identified them on the trail, it’s easy to see them on Owl Acres. They’re growing along the fence, at the edge of the fence rows, and wherever we haven’t mowed.
American bellflowers, (Campanulastrum americanum), also known as tall bellflowers, belong to the bellflower family even though their flowers aren’t bell-shaped, their scientific name comes from “campana,” the Latin word for bell. As the second part of their name suggests, these pretty wildflowers are native to North America, and range from the Atlantic to the Rockies.
These hardy wildflowers can grow up to seven feet tall on erect, central stems that are somewhat hairy to the touch. They have long, narrow leaves with toothed edges and pointed tips. The flowers are light blue, violet, or sometimes white. They have five petals that lay out in a star-shape, with a creamy-white ring at the throat. Petals are pointed and have wavy or ruffled edges. Each flower is about an inch across. They bloom in spikes at the top of the stems, starting with the lower flowers and moving up the spikes. The spikes of flowers can be up to 30 inches long at the top of the stem. Shorter spikes may develop at the base of the leaves near the top of the stem. The bellflower has a single taproot and is either an annual or perennial, depending on how warm the winters are where it’s growing. It likes rich, moist, well-drained soil and tolerates shade, growing in open woods, along stream banks, in ditches, and along my fence rows. By fall they will produce coppery-brown seed capsules loaded with tiny seeds. These capsules will dry and open, releasing those seeds on the wind.
American bellflowers attract a host of pollinators, including honeybees, bumblebees, sweat bees, wasps, butterflies, flowerflies, skippers, and even hummingbirds. As natives, they have evolved specifically to serve a particular long-tongued bee (megachile campanulae) that feeds only on the bellflowers. This bee has the usual four wings and six legs, large compound eyes, two antennae and large mandibles. It also has a long, tube-like tongue it uses to drink nectar. Only 8 to 11 mm (about a third of an inch) long, it is darker than others in its genus and less hairy.
Also known as resin bees, these specialized bees live solitary lives, and build individual nests out of resin instead of leaves. They nest aboveground in holes in wood or plants as well as in man-made habitats. They will sting if provoked, but the sting is much milder than that of a honeybee or bumblebee.
Several scientific studies have focused on how the American bellflower has adapted to climate change. Genetic mapping indicates that it originated in Virginia, some time before the last Ice Age. As the glaciers covered North America, they missed a few places including a highland plateau in the Appalachians. As the ice sheets receded and temperatures warmed, the bellflowers migrated northward and colonized new areas. It went something like this:
Imagine you are a bellflower seed flying on a south wind toward a more northerly place. You reach an area where none of your species has yet ventured. You land in the soil and germinate. You produce those lovely purple blossoms and try to attract bees. But the bees haven’t arrived yet. You ask the wind to bring you pollen, but there isn’t any out there—you’re a lone traveler. So what happens? Either you die unfulfilled, or you accidently self-fertilize. Self-fertilization is not ideal—you know that, but it will produce seeds, and some of them will be viable. The new seeds self-fertilize more readily, and soon you have become the progenitor of a new, adapted line of bellflowers. The only problem is that there’s no new genetic material to keep your strain strong. In fact, mutations creep in over time, and some of them are very detrimental to the bellflowers. Over time (thousands of years) the bees and the wind move north as well, and once again the bellflowers can cross-pollinate and strengthen their genetic materials. Another adaptation has arisen to limit self-fertilization by keeping the female part of the flower tightly closed until the male parts have dispersed their pollen. As our climate warms, the bellflower and other species will continue to adapt and some will fail. Happily, the bellflowers growing on Owl Acres are in the success category for now.
Photo by Author. Alt text: American Bellflower in the fencerow by the house. Frilly, purple, 5-petaled blooms adorn a vertical spike. The pistil (central female part of the flower) has a long style (stalk) topped by a 3-lobed stigma that catches pollen grains.