I received a comment from Susanne Davis who lives in New York, “I know every perennial’s job is to spread and ‘take over.’ I have battled all kinds of plants who have done their job better than I wanted them to do. However, this plant makes all the rest seem like slackers. This plant has choked out everything in its wake in several places in my huge cottage garden. Last summer was so hot and dry, I know I did neglect the gardens somewhat, but this spring, this plant created an emergency situation.
“Truly. I only garden organically, so I am spending day after day digging in my clay soil and re-planting the plants that are being choked out. I just spent my fourth eight-hour day, and I am not even half done. My husband worked for three hours today, and an experienced gardening friend spent three hours. I may need to hire help. Its leaves are absolutely everywhere. My back aches, and I am so very sorry I bought this plant not that long ago. I feel better knowing I am not alone.”
Creeping Bellflower
Creeping bellflower or European bellflower (Campanula rapunculoides) is a highly invasive flowering species. Ready-to-apply RoundUp is ineffective. Digging it out is relatively ineffective as well, since any little fragment of its taproot left behind will sprout a new plant. I have smothered clumps in my prairie with some success.

Creeping bellflower blooms look similar to the native harebell or bluebell bellflower (Campanula rotundifolia). But, unlike the native species, the 5-petaled, violet-blue bell-shaped flowers alternate up one side of its sturdy 3-4′ stem, and it produces new plants from its roots as it creeps along underground. Its serrated leaves have a broad base that narrows to a tip, and they seem to stay green all year long. It also reproduces by seed, so there’s a double-whammy in trying to keep it under control.

Native Bluebell Bellflower (Campanula rotundifolia) aka Harebell
The much more delicate-looking native bellflower’s violet-blue blooms, on the other hand, loosely cluster at the ends of the stems, often causing the plant to nod from the weight. The round basal leaves wither early, leaving only stems and blooms near the end of season. The native bluebell bellflower or harebell remains a single plant and reproduces only by seed.
Native American Bellflower (Campanulastrum americanum)

This biennial plant likes moist areas such as woods and wetlands. Its blue blossoms are more wheel-shaped than bell-shaped, and cluster along all sides of its hairy stem. It has a long, curving style, which protrudes from the creamy-white center ring.
Watch Out!
When purchasing or accepting plants, watch out for these! But as it often goes, along with the plants we want in our gardens, come plants we don’t want. They are currently listed under Wisconsin’s NR 40 Rule as regulated terrestrial invasive species.
Horrible to deal with. For a start, eat it! leaves, flowers, fleshy storage root. Mild taste. A friend’s grandmother called it her salad patch.
It’s good to know, Betty Jo — Donna
Do you have any tips on how to distinguish American Bellflower (Campanulastrum americanum) basal leaves from Creeping Bellflower (Campanula rapunculoides) basal leaves? To my untrained eye they look fiendishly similar! The flowers at least are easy to distinguish. With many thanks!
This no good way to tell the American Bellflower from the Creeping Bellflower, Laura, until the stems start to form. From the Illinois Widflowers:
American Bellflower: This plant is an annual or biennial from 2-6′ tall. Usually, it is unbranched, although sometimes a few side stems will develop from the lower central stem. The central stem is light green, terete, slightly grooved, and hairy. The alternate leaves are up to 6″ long and 2″ across, tapering to slender petioles. The leaves are medium to dark green, elliptic to ovate in shape, and their margins are serrated. The texture of the leaves is somewhat rough; they are hairy along the major veins of their undersides. The central stem terminates in a spike of flowers about ½–2′ long. From the axils of the upper leaves, secondary spikes of flowers may develop, but these are much shorter (about 1–6″ in length). The rachis (central stalk) of each spike is similar to the central stem.
Creeping Bellflower: This herbaceous perennial plant is 1½–3′ tall and little branched. The central stem is light green to reddish brown, glabrous to slightly hairy, and terete or angular. The alternate leaves are up to 5″ long, 2″ across, and variable in shape; the lowest leaves are often cordate-oval, while the middle and upper leaves are ovate-lanceolate to lanceolate. All of these leaves have crenate or serrated margins; their upper surfaces are medium to dark green, while their lower surfaces are light green and short-hairy along the veins. The lower and middle leaves have slender petioles, while the upper leaves are more likely to be sessile. Sometimes short leafy stalks develop from the axils of the leaves on the central stem.
Read: Definitions and Line Drawings of Botanical Terminology
I reviewed all kinds of reference materials, and this is what I gathered — Donna