Annuals or Perennials?

The echinacea coneflower is among perennials
that live for a long time.

By Lauren Sims
Photo by Alice Le Duc

As we prepare to flip to the next page on the calendar, we are reminded that spring is inching ever closer. That means it’s time to start thinking about our spring gardens, and one of our initial planting questions may be, “Annuals or perennials?”

Bill Cullina, author of Understanding Perennials: A New Look at an Old Favorite and other plant books, and director of horticulture at the Coastal Maine Botanical Gardens, would have us ask an even more fundamental question first: "What does it mean for a plant to be perennial, anyway?"

Often, says Cullina, people operate under the assumption that “perennial” indicates a plant that continues to grow and bloom for many years. While some perennials do last for generations, many of them only live for a few years. Perennial plants must store away enough energy to survive months of dormancy every year and regenerate the following season. This is a costly process, and many of the plant’s resources are invested in preparing for and living through this dormant period.

Annuals, on the other hand, have no need to store energy or conserve resources. They give everything they have for a short period of time, burning brightly but extinguishing quickly. The biological strategy for annuals is to produce the most seed possible.

“So it’s hard to find perennials that bloom the way an annual plant does or a tropical plant does, that doesn’t have to worry about stocking things away for the dormant season,” says Cullina, whom local gardeners may recall from his days as nursery manager at Chapel Hill's Niche Gardens.

“The idea of the non-stop blooming perennial, while there are a few things that might fall under that category, is sort of a pipe dream because when it’s blooming it’s using up its resources.”

To learn more about perennial plants and the design opportunities they offer, join Bill Cullina on Feb. 12 from 3-5 p.m. for “The Botany of Design” presentation at Duke Gardens. Cullina will also do a 9 a.m.-noon workshop for a small group titled “Beyond the Surface: Soil Demystified.”

The fee for “The Botany of Design” is $35; $30 for Gardens members. The soils workshop is $70; $55 for members. For more information or to register, please call 668-1707 or e-mail registrar Sara Smith. Please also see our online education booklet (PDF) for other discovery programs for adults and children.

Sarah P. Duke Gardens creates and nurtures an environment in the heart of Duke University for learning, inspiration and enjoyment through excellence in horticulture. The Gardens is at 420 Anderson St.

Lauren Sims is a graduate student at Duke Divinity School and a work-study assistant at Duke Gardens.