Whenever I worked in a nursery, I was always surprised by how many people weren’t sure what the difference was between annual plants and perennial plants and which one was which. If you shop for plants at all you should be aware of the difference because it affects how you garden. So I would like to help anyone who is uncertain to become familiar with these terms and to have a few examples on hand to remind them.
Annual plants go through their entire life cycle within one year. From seed to seed; they start from a seed, grow, flower, and produce seeds all in one growing season. Examples of annual plants are marigolds, zinnias, cilantro, lettuce, corn, and sunflowers. The Latin root annu means “a year”. We all know that annual means yearly, but it doesn’t mean an annual plant keeps going from year to year, it lives just one.
Perennial plants live for three or more years. This includes Oak trees, blueberry bushes, tulips, lavender, thyme, roses, and yarrow. The Latin root perenni means “through theyear”. Perhaps a good way to remember perennial is that they ‘persist’. If you have a perennial problem, it persists. If one has perennial beauty, one has it for the long term, not only for a year. So your perennial plants stay with you for a while, they persist.
Now, to make things a bit confusing, horticulturists commonly use the term perennials to differentiate the woody plants, the trees and shrubs (which are obviously perennial), from the more herbaceous (non-woody) perennials. These are the plants that have little to no woody growth. This category of perennials is loved for its flowers, and there are many. For example, lavenders, peonies, daylilies, the salvias, echinaceas, the bee balms, butterfly bushes, and so much more.
So, what would be an advantage of planting either annuals or perennials? Typically, the annuals offer a good color show all season long. Marigolds, zinnias, petunias and the like are used as seasonal color throughout the summer. Some of them need some deadheading (removing of spent blooms) to keep blooming. A disadvantage to planting annuals is that at the end of the summer they are all done for good. You must purchase new plants or start new seeds next year.
Perennials tend to have a shorter flowering time. Some, with a little deadheading, can be strung along for a little longer. My bee balm always starts blooming around the fourth of July, and I cut off the spent blooms to allow some side shoots to develop and open, but the show is pretty much over by August.
But then, some can bloom throughout the season. Some salvias can be in bloom for the entire summer. Salvia greggii blooms spring through fall and there are many varieties offering many colors to choose from. Salvia microphylla and the hybrids between the S. microphylla and S. greggii also bloom over a long season, and they’re all deer resistant, too!
The advantage of growing perennials is that they stick around for a fairly long time. You may spend a little more money on each perennial plant but they do reward you with their persistence. Because of their more permanence, their roots reach farther and deeper into the soil than annual flowers. This makes them more efficient water users and better at nutrient uptake. Many perennials are very drought tolerant and many are deer resistant, too. And many tend to attract and provide for bees, butterflies, hummingbirds, and beneficial insects.
Because of their more brief bloom time, perennials are usually put together in mixed beds so that new plants bloom when others have finished. Putting this tapestry together is a fun, yet forgiving, gardening project. There is maintenance to be done with them, you need to know when to cut them back, some need dividing every few years, sometimes a little trim for some deadheading. The herbaceous perennials die all the way to the ground in winter as in the echinaceas. And some are woodier, we call them sub-shrubs, like lavender and salvias, and they stay visible.
Did you know that tomatoes are actually perennials? Tomatoes, peppers, eggplants, and impatiens are some of the plants we call tender perennials. They come from warm frost-free climates where they are perennial but act as annuals here in our climate. So if you are lucky enough to have a greenhouse you can harvest some peppers and tomatoes year-round!
There is something between annuals and perennials. The two year plants are called biennial. The Latin root bi means “two”. So these plants take one year to start from seed, grow leaves and roots, and the second year they send up a flower stem and flower. If you have ever grown carrots or parsley and left them in the ground over winter, you will have noticed how they send up their flowers. The flowers of these plants, by the way, are very good at bringing in beneficial insects to your garden. Sweet William is a biennial, when we see it ready to bloom in the nursery, it is already a year old.
So just remember, annuals, biennials, and perennials live one, two, and three or more years, respectively.