What Is Perennial in Reference to Flowers?

Hardiness

• The hardiness of a perennial refers to its ability to survive winter temperatures. You can find your U.S. Department of Agriculture hardiness zone by referring to the zone map in the appendix of a gardening book or on the U.S. National Arboretum website. Choosing plants appropriate to your zone ensures that they have the potential to return year after year. Some plants, called tender perennials, survive the winter only in climates that don’t experience hard freezes. In cool climates, you can enjoy tender perennials by digging them up and bringing them into a frost-free structure for storage over winter or by replanting them each year as you would an annual.

Bloom Season

• Although there are perennials that bloom over a long period, the average perennial’s bloom season lasts only two to three weeks. For this reason, creating a garden of perennials requires careful planning to ensure that you always have something in bloom. Many gardeners use perennials with a long bloom season, such as purple loosestrife and threadleaf coreopsis, as well as garden annuals to fill in the gaps between bloom cycles. A few perennials, such as delphiniums and garden phlox, bloom again late in the season if cut back after their first flush of flowers.

Winter

• In winter, perennials do one of two things: They die to the ground with only the roots remaining alive, or they retain their leaves and stems. Those that keep their leaves are called evergreens, regardless of whether the leaves remain green or show colorful cool-weather foliage. Those that remain above ground keep the garden interesting in winter, but the ones that die back have a better chance of surviving in bitterly cold climates.

Maintenance

• Novice gardeners sometimes think they are saving time and effort by planting perennials. While it is true that you have to plant them only once, perennials require considerably more maintenance than annuals. Each type of perennial has its own specific needs and some need more attention than others, but regardless of the type of perennial, you can count on adding annual pruning and periodic dividing to your list of gardening chores. Pruning timing and technique vary from plant to plant. In general, pruning encourages strong growth and keeps the plant looking its best. Dividing prevents overcrowding. When a plant that has performed well in the same location for a few years stops blooming or begins to die in the center, it probably needs to be divided.