Named for a physician and botanist, and saddled with a species epithet reflecting a mistaken medical belief of colonial-era botanists, Lobelia siphilitica deserves to be considered on its own terms. It is a robust, clump-forming perennial native to eastern North America, growing three to four feet tall with flower spikes that are notably larger than those of related species. The blooms, a clear mid-blue, open from mid-summer into early fall and are particularly attractive to bumblebees and other long-tongued bees.

Moist to wet soil and partial shade are the conditions this plant wants, though it handles full sun well if the ground stays consistently damp. It will self-seed modestly and can be divided in spring as the clumps expand over time. In the garden it belongs near water features, in rain gardens, or at the back of a consistently moist border, where it provides late-season height and color when much of the garden is winding down.