Discreetly poking up amid the garden blooms is a many-roomed purple martin house in the style of a colonial dovecote. The shingle roof protects the structure from water; the finial makes an excellent lookout perch. Purple martins help control insects in the garden, and enthusiasts go to great lengths to entice colonies. Place your purple martin house away from trees and human dwellings, atop a pole for safety from predators. Paint the house white to keep it cool in the sun.