Five Things You Didn’t Know About . . . Annuals

The yellow-flowered melampodium brightens the landscape at the Glencarlyn Library Community Garden

The yellow-flowered melampodium brightens the landscape at the Glencarlyn Library Community Garden. Photo © Mary Free

by Mary Free, Certified Master Gardener

Unlike perennials, which live for more than two years, annual plants sprout, bloom, produce seeds, and die in a single growing season. If the garden was a stage, perennials would be the leads and annuals would be supporting performers. Colorful, long-blooming, easy care, and relatively inexpensive, annuals can be attractive additions to your pollinator garden.


But did you know?

1. Some plants that we treat as annuals are actually biennials or perennials.

Monarchs stop to feed on a collarette dahlia late season along their migration path to Mexico

Monarchs stop to feed on a collarette dahlia late season along their migration path to Mexico (from Creating Inviting Habitats). Photo © Mary Free

Ornamental perennials not viable in our hardiness zone and used as summer annuals include dahlia, impatiens (New Guinea), lantana, and verbena. Pansies are short-lived perennials used as a cool weather annual. Many plants harvested for food are grown as annuals. For example, parsley and carrots are actually biennials, which complete their life cycle in two years—flower and seed formation occur in the second year. Tomatoes and peppers are tender perennials. Along the southern California coast and in southern Florida, tomatoes can grow all year long. In colder areas, some gardeners may pot up a pepper plant or lantana, for example, and bring them indoors for winter or dig up the tuberous roots of dahlias and store them in a frost-free location. However, most people find these perennials most desirable as annuals for ease-of-care and the ability to switch varieties and colors from season to season.

2. Some annuals will reseed themselves and grow back the next season.

Jewelweed with Bumble Bee

Flourishing along Long Branch Stream in Arlington’s Glencarlyn Park, native annual Impatiens capensis (jewelweed) attracts numerous pollinators such as the bumble bee pictured above as well as hummingbirds, butterflies, other bees, wasps, and flies.
Photo © Mary Free

Natives like Ambrosia artemisiifolia (common ragweed, whose pollen is a common allergen) and Impatiens capensis (jewelweed, whose nectar is favored by butterflies and hummingbirds) are annuals that remain in the landscape by reseeding. Under optimum conditions, non-native ornamentals like cosmos, melampodium, and verbena may also successfully self-seed in Northern Virginia.




3. Some “annuals” can be invasive.

A common eastern bumble bee forages on Lantana camera

A common eastern bumble bee forages on Lantana camara growing in the Scented Garden in Alexandria’s Simpson Gardens. Photo © Mary Free

Cosmos bipinnatus (garden cosmos), an annual native to Mexico, provides nectar to a variety of bees and butterflies. However, because it can self-seed and naturalize, one must be wary of planting it where it can escape into the wild. Cosmos has been found to be invasive in parts of the Mid-Atlantic (including Suffolk City and Greensville, Prince Edward, Prince George, Stafford, and Hardy counties in Virginia and numerous counties in Pennsylvania). Lantana camara, native to the West Indies and the American tropics, is a tender perennial shrub grown as an annual in colder climates. But in Florida, it is considered an invasive exotic that has displaced or hybridized with native species.

Although we usually think of non-natives when we hear the words invasive species, some native annuals, like common ragweed and Conyza canadensis (Canadian horseweed, which behaves as both a summer and winter annual) are so efficient at self-seeding that they are considered noxious weeds in some states.

4. Some annuals can act as bridge plants in a pollinator garden.

Perennials expend a lot of energy developing their underground root systems often at the expense of flower production, reducing the duration of blooms. On the other hand, annuals, whose roots die at season’s end, can devote most of their resources to producing flower and seed. An annual’s extended bloom period ensures a continual nectar source for pollinators when perennials have yet to flower or are in decline.

5. Some annuals, despite their showy flowers, may not attract pollinators.

How do you know? If pollinators by pass your annuals or only stop on occasion, then there is probably good reason why. Oftentimes cultivars that are bred to appeal to humans, for example those with double flowers (i.e., with extra petals), achieve that appeal by sacrificing other traits (e.g., nectar may be of lower quality). Also, native pollinators prefer native plants that are suited to local conditions. Since many annuals are not native to the Mid-Atlantic Region, native species may not be attracted to them.

Have you assessed your gardens recently to determine how attractive they are to pollinators? If not, Pollinator Week, June 19–25, is a good time to do so. You also may want to use this time to visit the MGNV demonstration gardens to see how pollinators interact with a variety of flowers. If you are overwhelmed by the assortment of annuals in local nurseries, then look for our next posting: Five Annuals for a Pollinator Garden.

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