American Bellflower

All around my yard I have mini-invasions of the attractive-yet-aggressive perennial Creeping Bellflower, Campanula rapunculoides, with is tall raceme thick with 1” purple bells. This European import is prevalent in disturbed areas, but according to Forest Service, it is not believed to be a threat to undisturbed natural habitats. When I learned about a native bellflower that also produced tall flower spike I got excited and got hold of some seed. American Bellflower, Campanulastrum americanum, is a biennial, spends its first year as a rosette of foliage and then launches its flower spike, up to 5 feet, in the second year. Despite the similarity in the name, the American (or Tall) Bellflower is a very different plant from its creeping cousin. Its flowers are like sky blue stars rather than bells and very tall flower spike is rather leafy and not as densely populated by blooms. Also, American Bellflower reproduces by seed only and does not form underground runners.

The native range for Campanulastrum americanum is from Ontario to Minnesota and south to Florida. As such, there are not any native populations in Massachusetts. Its native habitat is in moist borders and open woods. While it may grow in full sun, it prefers cool conditions.

I put in seedlings in all parts of my yard ranging from dry shade to full sun in well drained soil, to see just how they do. These plants survived in all locations. In areas with fertile soil and lots of sun, the flower spike reached nearly 6 feet. In the dry shade it topped out at about 2 feet and did not bloom as intensely. It even survived under a Norway Maple. It does reseed itself quite well, where the seed can find good soil. I have way too many seedlings this year, but they are not so prevalent as I get with the Swamp Marigold, Bidens aristosa, growing in the same area.  By recognizing the rosette with its 1/2-1" heart-shaped leaves, you can mange the population by transplanting or removing excess plants.

The flowering period is from July to October. The first flush is strong then blooming continues slowly throughout the summer. While not as full as the first flush, these plants will produce fresh blooms later in the fall. I tried cutting some flower stalks back to generate new spikes at mid-season, but this was not too effective. Maybe this year I’ll try that earlier. Seed that is produced early in the season may ripen quickly and germinate to produce a rosette that year, essentially functioning as a winter annual.

Also of interest, C. americanum is on a list for plants suitable for use under walnut trees, having both resistance to the juglone and a tolerance for shade. Hummingbirds are reported to visit this plant and it has been used to treat coughs and respiratory ailments by the Iroquois and Meskwaki Indians.

Seed for C. americanum is becoming more available. I was able to get seed from both Prairie Moon Nursery and the New England Wildflower Society (NEWFS). In discussing native plants with Scott LaFleur of NEWFS, he felt that despite its vigorous nature in size and reseeding, this plant could do really well in the garden. From my experience I see that it may find its garden home in the back of a shady border or in a cottage garden, where it leafiness will blend in with the other masses of plants.  Since this plant is not native to the New England States, I would not recommend its use up here in areas near to natural areas where its seed may escape.