Many people are confused by the words “annual” and “perennial.” A good way to remember the difference is that perennial starts with “P” just like the word “permanent.”
A perennial plant or perennial flower is a non-woody plant that lives for more than two years. Perennials, especially small flowering plants, grow and bloom each season and then die back, returning the following year from their root stock rather than seeding themselves the way an annual plant does. These are known as herbaceous perennials. Which plants are perennial depends on the climate or “hardiness zone” where they are planted; some plants will be “annual” (lasting only one season) in a cold climate, but perennial further south.
Perennial plants can be short-lived or long-lived, and they can vary in size from only a few millimeters to more than 100 yards tall. They include a wide assortment of plant groups from ferns and sedums to orchids and ornamental grasses.
Unlike annuals, which produce seeds to create each new generation, perennials typically grow structures that adapt them to living from one year to the next. These structures include bulbs, tubers, rhizomes and woody crowns. They have specialized to survive under extreme environmental conditions: some have adapted to survive hot and dry conditions, others to survive under cold temperatures. Most perennials flower and fruit over many seasons in their lifetime. Annuals tend to produce many more seeds per plant since they will die at the end of the growing season, while perennials may produce less seeds but can produce them over many years.
In warmer and more favorable climates, perennials grow continuously. In seasonal climates, their growth is limited to the growing season. These plants are deciduous perennials. Re-growth is from existing stem tissue. Some perennials are evergreen, retaining their foliage all year round.
Perennial plants are usually better competitors than annual plants, especially under stable, resource-poor conditions, because they have larger root systems that can find food and water deeper in the soil. In spring, perennials are already established so they have a head start over annual flowers and weeds.
A big advantage of perennials for the home landscape is that they typically grow bigger and stronger each year, rather than having to be re-planted each spring. A variety of perennials in the landscape will improve all-season color by overlapping different bloom times in succession. Mixing perennials with shrubs gives the landscape more winter interest, since most perennials die back to the ground after frost. This mixture of shrubs and perennial flowers can have tremendous variety of color and texture.
Most perennials benefit from being cut back to the ground at least once a year. Some, like catmint and re-blooming daylilies, respond well to a mid-season scalping. In fertile soil they will quickly grow new leaves and then bloom heavily. Even a light shearing will stimulate many perennials to set new blooms. It helps to give them a shot of Flower Tone when you “deadhead” them or cut them back.
Steve Boehme is a landscape designer/installer specializing in landscape “makeovers.” He can be reached at 937-587-7021 or firstname.lastname@example.org.