Salvia mexicana 'Limelight'
This unusual tender perennial displays an electric color combination when its vibrant purple-blue flowers open from bright chartreuse calyces. Fortunately, glossy, bright green leaves hold their own until the show gets started in August (and continues until frost). It forms a tall bush, 6 feet tall by 6 feet wide, which is great for the back of the border. Salvias are some of the showiest plants for containers, annual borders, and mixed borders. Butterflies and hummingbirds love them.