Even in their dormant phases, perennial plants can die back to the ground, but their root systems are very much alive and the plants will continue growing when conditions are right.
What Is a Perennial Plant?
Perennials are plants that continue growing for more than two years, often featuring flowers. Perennials can be woody or non-woody, including some trees, many fruits and vegetables, and flowering plants. Unlike annual plants (zinnias, marigolds, radish) which complete their life cycle in one growing season, and biennials (Sweet William, canterbury bells) which need two growing seasons to mature and set seed, perennials are typically cold-hardy plants that will return each year in the spring.
A few perennials are considered to be short-lived, lasting only two to three years. Rose campion is a short-lived perennial, but because it self-seeds so readily, it appears to live much longer. Other perennials, like peonies, have been known to last for more than 100 years, though it may take several seasons before they establish.
Hardiness Zones and Perennial Plants
Not all plants with the ability to be perennial are hardy in all areas. Some can be killed by freezing temperatures, excessively dry conditions, or other growing problems. This is why hardiness zones are so important. Knowing what zone you garden in will allow you to determine what plants will survive in your area. Tender perennials, like begonias, elephant ears, and succulents, may overwinter in warm climates, while cold temperatures in northern zones can kill the plants entirely.
Types of Perennials
The term perennial is most often used for plants with showy flowers, but plants such as ornamental grasses, tropicals such as canna and caladiums, vegetables including rhubarb and artichokes, and other plants that have their own categories may also be perennial.
The term herbaceous perennial further narrows the definition of perennials to plants with soft, green stems that die back to the ground over winter in colder climates.
Trees and shrubs are considered woody or non-herbaceous perennials. They may lose their leaves in winter but remain very much alive in their roots right up through their stems, branches, and buds.
It's not always easy to tell a perennial from an annual plant unless you still have the seed packet or tag from the nursery pot. Besides the lifespan between the two, here are a few other hints:
- Perennial plants bloom for shorter periods of time than annuals.
- Perennials grow slower than annuals.
- Perennial plants may produce fewer blooms in their early years versus the showier blooms of annuals.
- You may also have an evergreen perennial that will keep its leaves year-round and does not die back in the winter like a herbaceous perennial.
Caring for Perennials
Perennials require different maintenance than annual plants, but they are not all carefree. Most require at least some pruning and feeding to remain healthy enough to survive several years.
- Division: Although you don't need to replant perennials every year, as you would with annuals, eventually most of them need to be dug up and divided to maintain vigor. Some plants need dividing every couple of years and some, like peonies, virtually never need division unless you want to make more plants.
- Pest Patrol: It's important to monitor your perennial plants regularly throughout the growing season for pests and diseases.
- Deadheading: Like many annuals, some perennials repeat bloom if you deadhead the spent flowers. Even deadheading the flower stems of non-repeat bloomers, like hosta and astilbe, ensures the plant directs its energy to its roots and leaves rather than to setting seed.
- Seasonal Clean-up: Prune and remove the old foliage from herbaceous perennials that die back in the winter to tidy the plant before the new growth begins. Some plants prefer to be cut back in the fall or spring, but check instructions so you don't inadvertently cut off forming flower buds.
Choosing Perennials for the Garden
Before purchasing perennials, observe the sunlight and shade patterns of the area you are planning for your garden or path. That way you can correctly select perennials that require sun or shade. Think about your wildlife population, too, because you may prefer growing deer-resistant perennials. In addition, since perennials bloom for short periods, make sure to integrate some interesting non-blooming foliage. Besides the plants already mentioned, here are a few more examples of perennials to choose from (be sure to know your hardiness zone before purchasing):
- Flowers: Coneflowers, ice plants, and Shasta daisies are all flowering perennials with longer bloom times than the average perennial.
- Shrubs: Azaleas and peonies are flowering perennial shrubs. Wintercreeper and false cypress are examples of non-flowering perennial shrubs.
- Groundcovers: Sweet woodruff and creeping thyme are flowering perennial groundcovers. Japanese pachysandra is a non-flowering evergreen perennial groundcover.
- Grasses: Most ornamental grasses are perennials, too, including fountain grass and pink muhly grass.