Lobelia fistulosa

From Brazil, this giant of a lobelia can send up flower spikes to over 2.4m tall!   It has large rosettes of green leaves which can reach over 90cm long in their first year.  The flowers typically form in the second year and are violet pink and tubular in shape.  Borderline hardy in milder parts of the UK - otherwise best brought in for the winter.  Well worth a try,