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Annuals make a landscape special. Like the decorations on a birthday cake, annuals provide the color and interest that take a landscape from everyday humdrum and make it more vibrant and alive.
Botanically, annuals are plants that germinate, grow, flower, set seed and die within one growing season. The growing season may occur during the warm season of April through October or during our cool season from October through April, depending on whether the annual is a warm or cool grower.
Perennials, on the other hand, can live for many years and do not die after flowering and setting seeds. Woody perennials include trees and shrubs and herbaceous perennials. Herbaceous perennials do not produce woody trunks and branches. They often die back to the ground during periods when they are dormant; they include such plants as lilies, cannas, ferns, Shasta daisies and chrysanthemums.
Horticulturally, we call plants annuals when they are attractive for or die after only one growing season. This includes many true annuals such as marigolds, zinnias, celosia, pansy, calendula and sweet pea. Many plants we think of horiculturally as annuals are actually tender (not hardy) perennials. They are grown as annuals because they will not survive the freezing temperatures of the average American winter. In Louisiana our winters are usually relatively mild, so many plants you see listed as annuals (for our Northern neighbors) may survive the winter and bloom another summer. Plants in this category include blue daze, coleus, dusty miller, lantana, ornamental pepper, periwinkle, pentas, purslane, salvia, scaevola, begonia, browallia and impatiens.
It is a good idea to keep these plants in mind when deciding what you want to plant and also what to pull up at the end of the year. A true annual, such as marigolds for instance, should be pulled up and discarded when ratty looking. Pentas, on the other hand, should be cut back in late summer and left in place.
Using annuals in the landscape requires some forethought. There are several points you need to keep in mind before you plant. Remember that annual plantings are high maintenance. The beds need frequent grooming, watering and weeding. Because of this, it’s usually a good idea to use annuals on a limited basis. Large, extensive beds quickly become a real chore to keep up.
Group colors together. The use of one or two colors in an area has more visual impact than many colors mixed together. When using more than one color, make sure colors compliment each other and their surroundings.
Colorful annuals should be planted where you want people to look. Directing someone’s attention to your trash cans by planting a row of petunias beside them is not a good idea.
Annuals may be grown from seed sown directly into the garden or put out as transplants you produce yourself or purchase at a nursery. There is generally a wide selection of both seed and transplants available at local nurseries and garden centers.
In October and November, we plant hardy cool-season annuals. These annuals prefer cooler growing conditions and will survive a normal winter with little or no protection (especially in south Louisiana) to bloom in the spring. Place these plants in a well-drained location in partial to full sun. Full sun produces more compact plants and maximum flowering.
Cool-season annuals for Louisiana gardens include alyssum, annual baby's breath, annual candytuft, annual phlox, bachelor's buttons (cornflower), calendula, Chinese forget-me-not, coreopsis, delphinium, dusty miller, English daisy, foxglove, geranium, hollyhock, larkspur, lobelia, blue bonnets, nasturtium, nicotiana, ornamental cabbage and kale, pansy, pinks (dianthus), Shirley and California poppies, scabiosa, snapdragon, statice, stock, sweet pea, toadflax and viola.
In April or May, the cool-season bedding plants finish and are replaced by warm-season plants. Warm-season annuals for sunny spots include abelmoschus, ageratum, amaranthus, balasm, blue daze, celosia, cleome, coleus (sun-tolerant types), coreopsis, cosmos, Dahlberg daisy, dusty miller, gaillardia, gomphrena, lantana, lisianthus, marigold, melampodium, narrow-leaf zinnia, ornamental pepper, periwinkle, pentas, portulaca, purslane, rudbeckia, salvia, scaevola, sunflower, tithonia, torenia (wishbone flower), perennial verbena and zinnia. Warm-season annuals for part shade to shady areas include balsam, begonia, browallia, caladium (perennial tuber), coleus, impatiens, pentas, salvia and torenia.