What Exactly is a Perennial Plant?

06/09/2018 | Ken Davis Flowers, In the Garden, Landscaping

By  Ken Lain, the mountain gardener


One of the top questions we get here at the garden center is “what’s the difference between an annual and a perennial?”.  The issue causes unnecessary confusion for novice gardeners, as it really is quite easy to understand.

Perennials are plants that can live longer than 2 years. They may go to seed every year, may die back to the ground in winter, but their root systems are very much alive and come back the following spring. Annual plants (geraniums, zinnias, marigolds, petunias, etc.) complete their life cycles in 1 growing season.   Biennials (Sweet William, hollyhock, snapdragon, dianthus…) need 2 growing seasons to mature and go to seed.


It’s important to know that perennials do not live forever. In fact, many perennials are considered to be short-lived, lasting only 2-3 years.  California Poppies are short-lived perennials, but because they self- seed so readily they appear to live much longer.

Hardiness Zones and Perennial Plants

Not all perennial plants are hardy in all areas. Some can be killed by freezing temperatures, excessively dry conditions, heavy soils, or other extreme growing conditions. This is why a garden’s hardiness zone is critical to a gardener’s data bank.

Knowing a garden’s zone allows a gardener to determine which plants will thrive in that area. Prescott and the surrounding areas are a USDA Zone 7, but we flirt strongly with zone 8.  That means we need plants that can survive temperatures below10 degrees F. Hardiness Zones

Different Types of Perennials – The term perennial is most often used for plants with showy flowers; but ornamental grasses, tropicals such as cannas and caladiums, vegetables like rhubarb and artichokes, and other plants in specific categories will thrive perennially.


Herbaceous perennials are those plants that will die back to the ground in winter and whose spent stems and foliage are pruned back level to the garden’s soil.  The roots of these perennial plants are alive and well all winter, with new growth emerging in spring.

Trees and shrubs are considered woody or non-herbaceous perennials. They may lose their leaves in winter but remain very much alive from their roots right up through their woody stems, branches, and buds. Perennial trees and shrubs are considered ‘woody perennials’.

Less work with annuals or perennials? – Perennials and annuals require different maintenance and nurturing. All are not carefree. Most require at least some pruning and feeding to remain healthy enough to survive several years.  I feed mine with Watters “All Purpose Plant Food” at least 3 times per year for guaranteed health and prolific bloom.

Division – Although perennials don’t need to be replanted every year, as annuals do, eventually they’ll need to be dug up and divided. Divisions can be replanted elsewhere in the garden. Some plants, like irises, need dividing every couple of years, while plants like peonies never need division except to make more plants.

Pest Patrol – Monitoring for pests and diseases is still very important with perennials. It’s bad enough to lose an entire season of annuals to a disease, but to lose a bed of perennials that have been in a garden for a decade is heart-breaking! Since perennials are usually planted in large clusters, it is very easy for diseases or destructive insects to affect an entire clump.  Perennials really need to be checked regularly throughout the growing season.

Deadheading – Many perennials will bloom repeatedly if their spent blooms are deadheaded regularly. This is a trait they share with some annuals. Even perennials that don’t repeat bloom, like hostas and astilbes, benefit from deadheading.  It allows the energy of the plant to go back into the roots and leaves rather than producing seed. Of course, if seed is desired, the seed pods may be allowed to form.

Seasonal Clean-up – Since herbaceous perennials die back to the ground each winter, they will need to be pruned and the old foliage removed before new growth begins in March. Some plants prefer to be cut back in the fall, while many prefer to be cut back in spring.  Most are not terribly fussy about timing, so they may be tended at the gardener’s convenience.

There are other maintenance jobs required by some perennial plants, but they are not labor intensive. Besides, these garden chores are at the heart of what it means to be a gardener.  Having some perennials in the garden is a great guarantee that there will be flowers each season, even if the gardener has limited time to plant annuals in the spring.

Summer Class Schedule has just been posted on the website.

June 16 @ 9:30am Fire-wise Landscaping – Beauty AND Safety – You can have a beautiful landscape while still protecting your home from wildfires. To make your landscape more resistant to fire, learn what “defensible space” is, and which plants are considered fire-wise. Some plants are more flammable than others and some plants even mitigate fire! By choosing the right plants we can diminish the possibility of fire, and still enjoy landscapes that enhance our homes.

June 23 @ 9:30am Landscapes that Add Beauty and Value – Did you know that that the right landscaping can increase your home value by more than 10%?  Carefully positioned trees can save up to 25% of a typical household’s energy usage for heating and cooling. Ken Lain will show students things that can add personality and value to a landscape. As the monsoons approach this is an ideal season to change the look and feel of your yard. Students learn tree placement, privacy techniques, ground covers, erosion control, inspirational bloomers, and more facts about landscaping.

June 30 @ 9:30am Totally Tomatoes! Grow the Best!  – The first of these most-prized fruits are appearing in the garden! Yes, this session goes deep on all things tomato. Students learn which varieties work best for their growing conditions and garden space, which bugs to watch for, diseases, companion plants, and garden advice that increases the year’s harvest.

Until next issue, I’ll be helping local gardeners pick the toughest plants here at Watters Garden Center.

Ken Lain can be found throughout the week at Watters Garden Center, 1815 W. Iron Springs Rd in Prescott, or contacted through her web site at WattersGardenCenter.com or  FB.com/WattersGardenCenter .

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