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?? It causes great confusion among novice, but you will quickly become a garden expert on the topic.
Perennials are plants that are expected to live longer than 2 years. Unlike annual plants annual plants (geranium, zinnias, marigolds, petunia and the like) that complete their life cycle in 1 growing season. Not to really make you and expert gardener . . .there are also biennials (Sweet William, hollyhocks, snap dragon, dianthus…) which need 2 growing seasons to mature and go to seed. Perennials may go to seed every year, and may even die back to the ground I winter, but their root systems are very much alive and come back the following spring.
The mistake some make is expecting perennials to live forever. In fact, many perennials are considered to be short lived, lasting only 2-3 years. California Poppy is a short lived perennial, but because it self seeds so readily, it appears to live much longer.
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, heavy soils or other growing conditions. This is why your gardens hardiness zone is so important.
Knowing what zone your garden is in allows a gardener to determine what plants will thrive in the landscape. 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 below10 degree temperatures.
Different Types of Perennials – The term perennial is most often used for plants with showy flowers, but plants like ornamental grasses, tropicals such as canna and caladiums, vegetables like rhubarb and artichokes, and other plants that have their own categories and do thrive perennially in local gardens.
Herbaceous perennial further narrows the definition of perennials to plants that will die back to the ground in winter and the spent stems and foliage are pruned back to the the gardens soil. The roots of these perennial plants are alive and well, and new growth will emerge from the ground in spring.
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 woody stems, branches and buds. Perennial trees and shrubs would be considered ‘woody perennials’.
Less work with Annuals or 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. Feed with Watters “All Purpose Plant Food” at least 3 times per year for increases success and bloom.
Division – Although you don’t need to replant perennials every year, as you would annuals, eventually they’ll need to be dug up and divided. These divisions are then replanted elsewhere in the gardens. Some plants need dividing every couple of years like iris, while plants like peony virtually never need division unless you want 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 you’ve had for a decade is heart breaking. And since perennials are usually planted in large clusters, it is very easy for a disease or feeding insect to affect the entire clump. You really need to check on your perennial plants regularly throughout the growing season.
Deadheading – Many perennials repeat bloom, if you continually deadhead the spent blooms. This is a chore they share with some annuals. Even perennials that don’t repeat bloom, like hosta and astilby, benefit from deadheading their flower stems. The energy of the plant can go back into the roots and leaves, rather than producing seed. Of course, if you want the seed, you can certainly allow the seed pods to form.
Seasonal Clean-up – Since herbaceous perennials die back to the ground each winter, you will need to prune and remove the old foliage, before the 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 you can do it whenever you have the opportunity.
There are other maintenance jobs required by some perennial plants, but they really are not labor intensive. Besides, these garden chores are at the heart of what it means to be a gardener. While perennials and annuals are not better or worse than one another, having some perennials in the garden is a great guarantee that you’ll have flowers each season, even if you have limited time to plant in the spring.
Until next issue, I’ll see you at Watters Garden Center.