The east Asian Platycodon grandiflorus (Jacq.) A. DC., Balloon-flower, self sows in some settings, and has been collected as "persisting...for several years" in a yard in St. Clair Co. It may eventually be found as an escape. It is ca. 4-8 dm tall with a showy bell-shaped usually blue corolla, distinctive in originating from an inflated, balloon-like bud.

1. Corolla strongly bilaterally symmetrical, 2-lipped; anthers fused, not separating after anthesis.

Lobelia

1. Corolla radially symmetrical; carpels 3; anthers coherent, separating after anthesis; capsules usually opening by lateral pores (except in Jasione).

2. Flowers in dense, involucrate heads, borne singly on stems leafless at least in the upper half; corolla divided nearly to the base into linear lobes.

Jasione

2. Flowers in spikes, racemes, or clustered, but not in dense solitary involucrate heads; stems leafy for their full length; corolla divided less than half its length into ovate to broadly triangular lobes. 

3. Corolla bell-shaped, with lobes shorter than the tube (except in the lax, scabrous, small-flowered C. aparinoides); flowers stalked (except in C. glomerata); perennial (biennial in C. medium).

Campanula

3. Corolla nearly flat (rotate) or broadly funnel-shaped, with lobes longer than the tube; flowers sessile or subsessile; plants annuals, winter-annuals, or biennials.

4. Flowers subtended by leaves or bracts linear or tapered to a petiolar base (not at all cordate); style at maturity bent down basally and then curved up apically.

Campanulastrum

4. Flowers subtended by ± cordate-clasping sessile bract-like leaves; style straight.

Triodanis