Lobelia erinus

Lobelias are small, long flowering perennials from South Africa. Lobelia erinus is a trailing species with masses of purple or blue flowers. It has fine stems and deep green leaves, which are toothed and roughly oval. It's especially effective in hanging baskets, flower pouches and other containers, where its trailing stems spill over the sides bearing masses of flowers, throughout summer.
 
Grow Lobelia erinus in a cool spot in moist soil in partial shade. Rejuvenate plants in midsummer by cutting back, to maintain bushy growth and encourage repeat flowering.