Perennials are plants that grow back year after year. There are some perennials like bulbs that you may have to dig up and replant the following year. There are many different kinds of perennials. They usually bloom at certain times of the year, some will bloom during the spring, some in the summer and some more towards the end of the summer. There are a few that bloom longer then others and some that have shorter bloom times. When planting perennials it's important to know the area that they are going, is it sun, part sun or shade and is the ground wet or dry. The height that you are looking for is also important because some perennials can grow 3-4 feet tall and spacing is important because perennials will get larger from year to year.