One of the best reasons to grow perennial plants is that you save time planting. While annual plants complete their lifecycle in one year and don't return the following year, perennial plants come back year after year—usually for a minimum of three years. Perennial plants are available in a wide range of size and colors. A few popular perennial plants include lilies, iris, ferns, hosta, coneflowers and ornamental grasses. When buying perennial plants for the garden, make sure they are suitable for your hardiness zone. Other factors to consider are 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.