Hello — my neighbour, who has a lovely garden, has given me a plant he calls “creeping European bellflower”. In trying to determine what conditions in likes my research turned up some dire warnings about something called “creeping bellflower” being very invasive, impossible to eradicate, etc. However, this plant did not have the “European” adjective in the name so I’m not sure if it’s the same thing. Before I throw this plant in the garbage I thought I would ask for your input. Do you know for sure, or should I discard it out of an abundance of caution?
What you are describing could certainly be the “Creeping Bellflower” (Campanula rapunculoides) that is considered a weed in Ontario, and although it can be difficult to identify a plant simply by a photo of its leaves, your photo supports this. Creeping bellflower has basal leaves that are heart-shaped and attach to the stalk by a stem, while the upper leaves are lance shaped and alternate, connecting directly to the stem. .
This perennial is sometimes called “European” because it was introduced from Europe as an ornamental plant. This website has some good photos that will help you to determine whether the plant you have been offered is Campanula rapunculoides. Variously described as a weed or a wildflower, and considered to be an invasive in nearly every province in Canada, this is a plant that is almost impossible to eradicate once it takes hold in the garden, as it spreads by both a system of underground rhizomes and by seed. It seems unkind to reject an offering from a neighbour, but unless you are absolutely certain that what you have been given is a different variety of bellflower or harebell (and most other varieties have very different foliage), it makes sense not to introduce it into your garden.
Here are two excellent descriptions of creeping bellflower with good pictures Campanula rapunculoides page , Campanula rapunculoides (Creeping Bellflower): Minnesota …
I would suggest leaving it in the pot and wait for the flower stalk and flowers to fully develop then compare it to the pictures before deciding whether to plant it or not.