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Annual, Perennial... or Temperennial?
First published on garden.org on May 21, 2009, by Suzanne DeJohn
Many plants that are labeled and sold as annuals are actually perennial -- just not in our harsh Northeast climate. As you probably know, a true annual completes its life cycle in one growing season. A seed germinates and grows into a plant, which flowers, sets seed, and then dies. Marigolds and zinnias are examples of true annuals. Perennials live for more than a year in suitable climates. Geraniums (Pelargoniums), petunias, and sweet potato vines are perennials but are sold as annuals because they aren't winter hardy in much of the country.
It's All Relative
As more and more plants are bred from tropical and semitropical parent plants, the distinction between the terms perennial and annual continues to blur. Begonia, callibrachoa ('Million Bells'), coleus, diascia, impatiens, nemesia, osteospermum (African daisy) -- all perennials that are commonly sold as annuals.
What does it matter? Because, if you're so inclined, coleus, geraniums, and petunias can be overwintered indoors, remaining alive -- if barely in some cases -- to be replanted the following spring. And as a student of botany, it annoys me when I read about hardiness zones for annual plants. (If a plant dies at the end of the growing season, the hardiness rating, based on the average minimum winter temperature, is irrelevant. If the zone IS relevant, then the plant isn't an annual, it's a tender perennial.)
Because most "bedding plants" like petunias and impatiens are grown far away and shipped nationwide, I suppose it makes sense that growers just label tender perennials as annuals, rather than having to customize labels and train store personnel in the nuances of region and hardiness. For example, after a few years of living in North Carolina I realized that Verbena bonariensis is perennial to zone 7 and would come back each spring. In zones 6 and colder, the plant won't overwinter outdoors so to be on the safe side it's usually labeled as an annual. 'Million Bells' callibrachoa is rated hardy to zone 9, but came back in my zone 7 garden.
Althought the distinction is less relevant here in Vermont, where far fewer plants will survive the winter, I still like to know if a plant is an annual or perennial. (Inquiring about plant hardiness here is a little like having to ask the price of something. If you have to ask, you can't afford it. In Vermont, if you have to ask about a plant's hardiness, it's probably not hardy.) I suppose I just want to know whether I can justify the expense of a plant if there's a possibility of keeping alive indoors over the winter.
An Honest Relationship
The term "temperennial" has been coined to describe these tender perennials so often sold as annuals. The term calls to mind relationships and expectations. Is this a one-time summer fling (zinnias) or a lifetime commitment (peonies)? Or something in between (geraniums)? Spring is a time of anticipation for gardeners, as we survey our landscape for signs of returning life. We expect to pull up and replant annuals, but a perennial that doesn't return represents a loss -- and even a failure to those who take their gardens very personally.
Angel's trumpet (Brugmansia spp.), banana, calla, canna, elephant ear (Alocasiaspp), helicrysum, heliotrope, jasmine, mandevilla, Mexican heather (Cuphea spp), passionflower, pineapple sage (Salvia elegans), tibouchina -- these temperennials swagger in to stun us with their showy, exuberant growth in spring and summer. Then they decline in fall and we wonder, is it worth trying to save them? Will the endure indoors long enough to make it to next spring? If they don't, well, we kind of expected that. If they do, then they can have a piece of our heart for another season. No lifetime commitments here.