This week's Plant of the Week, the American Bellflower (Campanulastrum americanum) I noticed on a walk along the prairie at the Apple River Fort Museum in Elizabeth. I was struck by the blue color of the flowers, but wasn't sure exactly what it was, so I pulled out my trusty Illinois Wildflowers book by Don Kurz and identified it.
American Bellflower is an annual or biennial plant that grows to about 2-6' tall depending on the soil moisture and fertility levels. This particular group of plants was pretty happy in it's location and was about 5' tall and sprawling. I've learned that these plants can easily remain in their location by self-seeding. The point at which the seeds germinate generally determines whether the plant will grow as an annual or as a biennial.
The preference for this plant is in light shade to partial sun, which is exactly where this was growing along the treeline. It grows best in moist to mesic conditions, and a rich loamy soil.
The flowers of American Bellflower were what drew me to it. Flat, star-shaped, five-lobed, light blue flowers (to 1" across), each with a distinctively curved and recurved style and a pale white ring at the throat, bloom solitary or in clusters at the leaf axils in summer (June-August).
Missouri Botanic Gardens notes that plants in the genus Campanula usually have bell-shaped flowers (from Latin campana meaning little bell). This bellflower is one of the exceptions, however, in that it has flattened rather than bell-shaped flowers. These flower differences have in large part resulted in the recent reassignment of this plant by some authorities into a separate genus under the name of Campanulastrum americana.