American Bellflower Update

American Bellflower, in bloom from
late June through August

Over a year ago I posted some information on the American Bellflower, Campanulastrum americanum.  This plant, or it's progeny anyway (it's a biennial) have been growing in my yard since 2008.  It spends its first year as a rather innocuous rosette of leaves, but in its second year it shoots up to form a flower stalk between 2 and 6 feet in height, depending on location.  This spring I had an over abundance of second year plants within about 5 feet of the 2009 plants that I let go to seed. This spread is consistent with the smooth round seed just falling to the ground from the tall flower stalks.  Not wanting to throw any of these seedlings out, I redistributed them to a variety of areas in my yard that are normally difficult for growing flowering plants. 

A spontaneous composition on
the edge of the driveway with
Spiarea latifolia, the blue
Campanulastrum and
Rudbecia hirta.

The Campanulstrum growing in
dry shade under a Crabapplealong a foundation.

Along the North side, here the Hostas
hide the legginess of the Bellflower



Growing in rocky soil from under the
deck - plants forming a screen.



It seems that the plant looks better in some of the more challenging locations, where its vigor is moderated.  In rich soil with lots of sun it can become a floppy 6 foot monster.  Some places where it is doing nicely are : cracks in the driveway, a sterile rocky area under a deck, north side of the house, under a Norway Maple and in the deep shade of a Crab Apple along a dry foundation.  I think this latter location shows the American Bellflower at its best.

As far as pollinators, it seems that there is one particular bee, probably a type of Mason or Miner Bee (can anyone ID this for me?), that really loves this plant.  The first couple of years I didn't see much action with bees, but this year the bee activity has taken off!  A few larger bumblebees drop in, but they prefer the Meadowsweet (Spiarea latifolia var. alba) for the most part.

The meadowsweet is preferred by the bumblebees

I have been a little concerned with how vigorously this plant reproduces, however it is fairly easy to pull up so it can be controlled in the garden fairly easily.  It is not as aggressive a reseeder as my Bearded Beggarticks (Bidens aristosa), which I am glad to say is easily edited out by selective pulling.  The question of persistance of the seed remains.  How many years will it lie dormant in the soil? 

Also, since this bellflower is not a Massachusetts native, I wouldn't recommend its use near wild areas in this state.  But I do think it works well as a North American native that is well adapted to the conditions of the modern residential landscape, particularly under trees and along shady foundations.

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.