When you grow perennial plants, you'll spend less time planting and more time enjoying your garden. Perennials are plants that come back year after year—usually for a minimum of three years, while annual plants complete their growing cycle in one season and then die. A few popular perennial plants include lilies, iris, ferns, hosta, coneflowers and ornamental grasses. Before buying perennial plants for the garden, make sure they will grow in your grow zone. Also, consider how much daily sunlight they need, what type of soil they grow best in, their mature height and spread, harvest or bloom time, flower color (if applicable) and other growing requirements.