"Perennials" come from nearly all the plant families of the world. Chrysanthemums, lilies, daisies, hostas, grasses, and thousands of other garden lovelies are in this group. Perennialis a functional term. It generally refers to plants that appear to die every year, only to grow big and beautiful again after a rest period. While resting, the plant is "dormant." For the majority of perennials, the rest period (dormancy) happens during the winter. The plant's leaves may wither and dry. To our view the plant looks dead, or nearly so — a few bits of green might struggle on through the cold. On some internal schedule, the plant uses energy in its root system to bring forth a new display of stems, leaves, and flowers. And while we often feel winter is the cruelest season, summer too can be stressful on plants. A number of perennials go dormant in the hottest part of the year, reserving their energy for gentler spring and autumn.
When surviving dormancy, some perennials are tougher than others. The degree of cold that particular plants can survive does vary. Perennials are studied and rated according to their ability to withstand freezing temperatures, and this rating is called "hardiness" or a zone rating. It is one of the most basic pieces of information given in perennial descriptions, right up there in importance with sun exposure and moisture needs. Your local nursery will offer perennials that are expected to live in your area. Mail order plant sources can lead you to exciting new possibilities but it's up to you to remain aware of your zone hardiness rating in order to wisely choose from unfamiliar perennials. FInd your zone at this link, if you don't already know it.
Perennials are no more mysterious than annuals. They return year after year, increasing in beauty, and can be spread (or grow by themselves) to fill larger areas.
Aquilegia (Columbine)name unknown
The fact that perennials live year to year makes them semi–permanent (unless you decide to remove the plant, or it is totally unfit for its site.) You'll only have to buy that plant once, but you can move it later in its life, and you'll enjoy it for decades. Perennials are usually the bigger plants in the garden store. (Small multi-packs hold annuals, which have to be bought new every year, but that's another article.) Perennials cost a little more, in keeping with their larger size. Bigger plants take longer to grow and cost more to ship than tiny annuals. You might like to browse mail order sources of perennials. You'll see more choices that way, but will have to be an educated consumer. Pictures on nursery websites show the ideal display of the plant, not what you'll actually get in the mail! It might be wise to remember that you often "get what you pay for". Many Dave's Garden members check the Garden Watchdog before placing their first order with an unfamiliar company.
Any spot in the garden is suitable for some perennial. There are perennials for all conditions, from dry and sunny to moist and shady, dry and shady to moist and sunny. Yes, you do need to be aware of some basic conditions in your garden, but no more so than when choosing annuals. Perennials offer some of the most striking floral displays in cultivation, (ahh, peonies! Irises!) but they usually don't last all summer long; most perennials are only in bloom for a few weeks of the year. This means that planning and using a mix of perennials is important in keeping some color going through spring, summer, and fall. The use of plants with varying leaf shapes, size, color, and texture can really liven up a bed of perennials even when none are in bloom. In fact, some favorite perennials, like hostas and ferns, are used primarily for their foliage.
Perennial gardening opens up new aspects of plant management, maybe to the point of fussiness. Many need a cleanup as they go dormant (as do annuals at the end of their life.) Most perennials suffer to some degree without periodic (maybe every three to five years) dividing and replanting. It's up to us to decide whether more garden tasks is a good thing (I vote yes.) But often gardeners really do enjoy the an excuse to dig, divide, and move plants around in search of the perfect site. With proper care and feeding (similar to that for annuals,) nearly all perennials grow without limit and live virtually forever. For those reasons, perennials are very share-able. Your favorite plant may become a loved garden choice for a friend, or become an heirloom to pass along to family. It's a rare gardener who doesn't have Mom's daylilies or Grandma's peonies, for example.
There are entire books devoted to perennials. There are even entire books devoted to only certain perennials. All you really need to know to get started is that "perennials" are no harder to grow than simple basic annuals.