A potentially large shrubby species (6ft tall here) from Chile with vivid scarlet flowers, and remarkably hardy so far. I've planted these outdoors in several locations in Sussex (all sunny and well drained) and they've formed substantial clumps.
This year, with the mild winter, they've been evergreen and flowered on last year's stems. In colder years they are cut to the ground by frost but grow away vigorously in the spring and flower in August. For any well drained soil in full sun.
Barry Clarke, the holder of the national collection of Lobelia, tells me this probably isn't excelsa, in which case, as far as I'm concerned anyway, it's even more interesting.
Another large Chilean species more like the better known L.tupa but more shrubby. The flowers are a dark maroon red in this case. These seem to be much less hardy than excelsa but would make a good subject for a container in cooler areas (as here) or in a sheltered spot in perhaps the South West or elsewhere in Europe. I'm going to plant some in a garden in Rottingdean - see how that goes.