Blue trumpet vine

This is a fail-safe, showy, evergreen climber grown for its heart-shaped, dark green leaves and yellow-throated, bluish summer flowers. Grow in a border where its roots can spread, rather than a pot, and it'll be even more prolific. If the temperature is kept over 13C, and plants get bright, filtered light instead of full sun, there's a good chance it'll flower all year. Prune in spring if it gets out of hand. It has been given the Award of Garden Merit by the RHS.