Annuals, Perennials and In-Betweens

You’ve heard the terms "annuals" and "perennials", and may find them more confusing than helpful. Here’s a cheat sheet to provide a little background, as you create your own custom garden.

Annuals

These are plants that do it all in a single year; they complete the life cycle of growing, flowering, setting seed and then dying.

Or, these are plants that can't manage the winter cold in your region so they die if left outdoors. It's worth noting that these same plants might not be annuals in a milder climate.

A good example is cosmos. These feathery foliage summer bloomers die end of the growing season. You may find baby cosmos next spring in the place where they grew this year, but those are seedlings. The parent plant doesn't resprout.

Perennials

Assuming basic cultural needs are met, these plants will overwinter outdoors and regrow in the spring. Some perennial plants live an average of less than 5 years (columbine and Black Eyed Susans) and some persist for a solid fifty (peonies). Either way, their life cycle circles for years, with a number of spring reappearances to be expected.

In Betweens

Like the exotic fruits and vegetables in the grocery produce department, garden plants come to us from all over the world. Many of these, in our climate, are tweeners, not really annuals and not fully winter hardy perennials. Here are some of the categories that have been developed to group these not-quites.

  • Biennials - These plants sprout, grow and die back in the first year and grow, flower, set seed and die in the second year. They live for two growing seasons but bloom just once. Not surprising this hurts their standings on the popularity list. Parsley, Sweet William and some hollyhocks are examples of biennials.
  • Hardy Annuals - These are annuals that can survive a frost or two. In years with mild winters, they may survive, put on new growth in the spring and carry on through the rest of the season like nothing unusual occurred. Examples of hardy annuals are alyssum, violas and dianthus.
  • Tender Annuals - These plants swoon if the word "frost" is whispered and generally can't handle temperatures colder than 50-55 degrees F. Begonias and impatience are good examples.
  • Tender Perennials - Don't let the word "perennial" in this group's name fool you; these plants are perennial in only the warmest parts of the U.S. Callas and caladiums, winter hardy to zones 8 and 9 respectively, are considered tender perennials in the U.S.
  • Tender Bulbs - Tender bulbs are those that likely originated in a sub-topical or tropical region and require warm winter temperatures to survive outdoors. Unlike daffodils and hyacinths, tender bulbs - such as amaryllis, dahlias and cannas - cannot be expected to survive if left in the ground anywhere winter temperatures drop below freezing.

Choices: Why Grow Annuals?

Because annuals have a single season to get the job done - for plants that means keeping the species going – they have to flower and develop seeds for the future during a single growing season. They are genetically programmed to bloom aggressively because seedpods follow flowers, and seeds are the goal. To decorate or landscapes, we're more interested in the flowers than the seeds, but the two go together.

(Maybe you've heard about trimming off spent flowers to encourage ongoing blooms; this is the logic behind that. The dried up flowers on annual plants send a chemical signal out to the rest of the plant that says "Hold up on the bud and flower production. We've got seeds developing and have done our job. Time to rest.")

The short and simple takeaway is that annuals produce lots of flowers. And that's generally true. However, you have to replant every season. Of course, that lets you experiment with new varieties every spring – how awful is that?

Choices: Why Grow Perennials?

Perennials come back year after year. Spring's warm weather prompts sprouts and before you know it, the garden is full of foliage and blooms again. Typically, perennial plants flower for a few weeks each year, not from spring all the way through fall. A bit of planning is required to have good splashes of color for the entire season. The upside is that this allows colors palettes to change with the seasons.

We know an experienced gardener who focuses on pink, purple, blue and white perennial flowers in the spring, a wild mix of colors in mid-summer, and reds, oranges, golds and yellows in the fall. Creating a garden that's this carefully planned is likely more involved than many folks would choose, but you get the idea. Options are good.

Also, one can make the case that perennials can be more cost efficient because they don't need to be replaced every growing season. Some, like hostas, lily of the valley, cranesbills and daylilies can be divided every 3 to 4 years and replanted to expand the garden.

Mix It Up

Most people find themselves choosing to create custom landscapes that blend annuals, perennials and others. This offers maximum variety, the ability to tweak based on last year's learnings and lets one incorporate that just-introduced new plant with the purple ruffled flowers and striped leaves. Yippee!