Cool-Season Annuals by Rita Pelczar

New varieties keep gardens blooming through the fourth season.

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Cold weather needn’t signal the end of your flowerbed displays. Heat-loving zinnias and tender impatiens have long since succumbed, but there are bedding plants available to fill those gaps. A few will bloom throughout winter; others will persist, poised to burst into bloom with the first breath of spring.

Limits of Latitude

Of course, the selection of cool-season annuals as well as their blooming schedule varies significantly from one region to another. In regions with little or no freezing weather, January annual displays rival those in June, and while different species are appropriate for each season, there are plenty of choices for each.

In fact, many of the plants that northern gardeners consider staples of their summer beds and window boxes, like petunias and geraniums, are grown as “winter annuals” in warmer climates. “Our plant palette is completely different in the winter and summer,” notes Heather Will-Browne, bedding plant specialist at Walt Disney World in Orlando, Florida. On a recent summer trip north, she was amazed at the plant combinations she saw. “Petunias with portulaca!” she marvels. “That would never happen here—it’s two completely different seasons for us.”

The term “winter annuals” is not strictly accurate, since some of the plants lumped into this category are biennials (living through two growing seasons) or short-lived perennials. But they generally are treated as annuals, and like true annuals, they bloom the first year from seed. When their performance goes downhill as temperatures rise in late spring and summer, they are removed and replaced by heat-loving species until fall, when they are replanted for another cool season.

The selection of winter annuals for areas that experience fairly mild winter weather goes well beyond the ubiquitous pansies and ornamental kale. Stock (Matthiola incana) bears flowers in a wide range of colors, all of which impart their spicy-sweet fragrance to the cool-season garden. Flowers of the pot marigold (Calendula officinalis) are limited to yellow and orange hues and tolerate frost and even a light snow. Other potential season extenders for regions with mild winters are osteospermums, toadflax (Linaria spp.), felicias, and wallflowers (Erysimum spp.).
As you head northward into cooler climes, the selection of winter annuals is more limited. But even where freezing temperatures and snow cover are regular players on the winter stage, there are a few bedding plants that will add color to gardens through much of the cool season. Some will extend the fall flower display until Thanksgiving or later, and some will jump-start next year’s garden come spring.

The “Big Five” winter annuals

The most popular winter annuals—and, not surprisingly, some of the most cold tolerant—are pansies, violas, dianthus, snapdragons, and ornamental kale. University of Georgia horticulture professor Allan Armitage, an American Horticultural Society Board member and author of several books on annuals and perennials (see “Resources,” page 30), calls these plants “the big five.”

All persist through some frost and freezing temperatures, although varieties differ in their ability to handle the cold. It should be noted that surviving low temperatures is not the only objective. In order for them to warrant a place in your garden, they must not only survive, but remain attractive, at least far enough into the cold season to put on a good show.

Pansies and violas

It’s easy to understand why pansies (Viola 5wittrockiana and hybrids) are referred to as the king of winter annuals. They bear their distinctive and cheerful five-petaled flowers late into fall, sometimes through winter, and then burst into full glorious bloom very early in spring. Pansies can flower when the thermometer dips into the 20s and will tolerate even colder temperatures, surviving winter as far north as USDA Hardiness Zone 6 or even 5, with some protection. “Nothing comes close for winter and early spring bloom,” says Armitage.

Bob Lyons, director of the JC Raulston Arboretum in Raleigh, North Carolina, concurs. “The best flowering annuals for our winters are pansies and violas, with my favorite being the latter.” Most varieties flower all winter in Raleigh, experiencing only “an occasional decline when it gets its coldest here in January and February,” says Lyons.
This chilly persuasion isn’t surprising, given their lineage; pansies were named for the Swedish botanist V.B. Wittrock, who did extensive breeding work on them in the late 19th and early 20th centuries, crossing and backcrossing several viola species, all alpine natives. Pansies are actually biennials or short-lived perennials, but they are commonly grown as annuals.


Photo credits: Dynasty dianthus and Viola 'Sorbet Lemon Swirl' both courtesy of Ball Horticultural.

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