First, what is an air plant? Air plants are in the bromeliad family. The air plant genus Tillandsia (tih-LAND-zee-ah) is the largest in the bromeliad family. The names tillandsia and air plant are often used synonymously and many affectionately call them Tillys. There are a couple of major differences between tillandsias and the other bromeliads. Most bromeliads have tightly fitting leaves that hold water in a reservoir at the center of the plant. Many tillandsias also have this “rosette” shape, but care must be taken because if water is retained too long in the center of the plant, it can cause the plant to rot and die.