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Mad About Annuals
Scott D. Appell
Light-years ago, when I was renting a small house in Columbus, Ohio, while continuing my graduate studies in horticulture, I made a momentous discovery. I fell madly in love with annuals. I realized that by using these plants I could perennially (no pun intended) transform the plantings on my quarter-acre property. I could modify the color combinations willy-nilly, create ever-changing garden designs, devote entire beds, borders, or containers to annuals with specific purposes: blooms destined for fresh-cut flower arrangements, for example, or candidates for dried floral designs intended as holiday gifts. When I was forced to work a third-shift job to augment my meager student budget, I created an evening garden and delighted in its nocturnal beauty and fragrance. And when I had major travel plans, no problem—I'd devise a planting of drought-resistant annual beauties. Ever since, I have experimented with newly introduced annuals at my caprice, every single year. Annuals have long been called "the gardener's palette" by virtue of not only their versatility but also their infinite variety of colors and forms. Annuals make it possible for any gardener to become a horticultural Vincent van Gogh.
The flower spikes of pink and purple larkspur, Consolida ajacis, frame the showy bright pink blooms of lavatera and clarkia.
During the decades since my grad school days, there have been enormous changes in the world of annuals. Intensive breeding programs, extensive cultural trials, and the advent of tissue culture have brought us innumerable exciting new varieties. At the same time, the term "annual" is being used much more liberally, increasing choices even more. A number of confusing variations on the word "annual" have become popular in nursery catalogs and gardening literature. Most are references to plants used as annuals in the garden, at least in cool climates, but that are not true annuals in the botanical sense of the word.
In order to demystify what qualifies as an "annual plant" these days, let's take a look at the container planting on the facing page, a terra-cotta pot brimming with sensational, cutting-edge annuals. The planting is indeed a magnificent sight to behold, but the botany behind it is as interesting as the plants themselves. They include both true annuals and plants that, technically speaking, are not true annuals but are used as annuals nowadays, especially in cool climates.
True Annuals
The chartreuse-flowered Zinnia elegans 'Envy' in our planting is the only example of a true annual. Botanically speaking, annuals are plants that complete their life cycle—growing from seed, flowering, setting seed, and dying—within one growing year.
Hardy Annuals
The snapdragon, Antirrhinum majus 'Black Prince', in actuality a short-lived perennial, is known in horticultural circles as a hardy annual because it can tolerate light frost and even a little snow. In fact, when cultivated in warm regions or in a protected site in cooler areas, it can even overwinter and bloom the following year. Dusty miller (Senecio cineraria) is often listed in this category as well because it can overwinter quite happily in cool regions.
Half-Hardy Annuals
Plectranthus argentatus, an evergreen shrub native to Australia, is often termed a half-hardy annual by horticulturists; this implies that it can be set back, damaged, or killed by continued exposure to frost, but a few light frosts will not harm it.
Tender Annuals
The coleus, Solenostemon 'Palisandra', and the licorice plant, Helichrysum petiolare, are all considered tender annuals. Native to warmer parts of the globe, they are killed by the first frost. Of course, in their countries of origin, and in the warmest parts of North America, they are perennial and live more than one year. The taro, dahlia, and ornamental sweet potato are tender annuals too; they are also tuberous plants, which means that in cool climates, after frost has killed their tops, the tubers can be dug up, stored over winter, and replanted when the soil warms up the following spring.
Tender Perennials
The variegated Mauritius hemp, Furcraea foetida 'Mediopicta', is one of another group of plants used as annuals in cool climates, called tender perennials. This horticulturally vague term implies that these plants will flourish happily outdoors during the growing season but need to be overwintered indoors in temperate regions. Like the plants known as tender annuals, they are perennial in their native habitats, where they may grow into huge specimens.
No matter how these plants are categorized, they are all used as annuals in all but the warmest North American climates. They are also some of the most spectacular plants to be cultivated in any situation. So read on and discover how you can use annuals in your garden to become a horticultural Monet or Matisse.
Different Types of Plants Commonly Used in Annual Displays
- Solenostemon 'Palisandra', coleus, tender annual
- Plectranthus argentatus, half-hardy annual
- Senecio cineraria, dusty miller, hardy annual
- Colocasia 'Black Magic', taro, tender annual
- Dahlia 'Bishop of Llandaff', dahlia, tender annual
- Zinnia elegans 'Envy', zinnia, true annual
- Antirrhinum majus 'Black Prince', snapdragon, hardy annual
- Furcraea foetida 'Mediopicta', Mauritius hemp, tender perennial
- Ipomoea batatas 'Pink Frost', sweet potato, tender annual
- Helichrysum petiolare, licorice plant, tender annual
Scott D. Appell has written four books, Pansies, Lilies, Tulips, and Orchids. In addition, he is the editor of Brooklyn Botanic Garden handbooks Landscaping Indoors (2000) and The Potted Garden (2001). He is former director of horticulture at the St. George Village Botanical Garden in St. Croix, U.S. Virgin Islands; a past member of the Publications Committee of the Pennsylvania Horticultural Society; and a board member of the American Violet Society. His private consultation company is called The Green Man™.
Photo: David Cavagnaro; Illustration: Emma Skurnick