Volume 46 Number 1 Spring 1999



Summer Selections:
Summer Bedding Plants Evaluated for Alabama
Landscapes

 J. Raymond Kessler, Jr., Bridget Behe, and James Bannon

Gardening consumers often are bewildered by the wide range of flower colors and types of summer annual bedding plants available in the retail market. Consumers also are often disappointed because they purchase varieties (cultivars) that don't perform well in Alabama's hot, humid environment and throughout the area's long growing season. To help consumers and plant retailers know more about the best bedding plants for summer, AAES researchers evaluated the performance of more than 300 cultivars from 23 different bedding plant species during the summer of 1997.

Consumers typically purchase warm-season bedding plants from late March to May for planting in commercial and home landscapes. The majority of bedding plants are purchased in plastic market packs from garden centers, grocery stores, mass market outlets, and home centers. These retail outlets maintain large displays containing a wide selection of bedding plants in a variety of types, plant sizes, and flower colors.

Extended periods of hot, humid weather; periodic violent thunder storms; and periods of drought all can take their toll on bedding plants, making it difficult for some traditional bedding plants to remain healthy and flowering (floriferous) throughout Alabama's long growing season. Many petunia cultivars, for example, develop unattractive elongated, spindly growth and sustain damage to delicate flower petals from strong wind and rain later in the season. Older cultivars of zinnia contract foliar diseases, such as powdery mildew, during humid weather causing lower leaf loss. Most bedding plants require at least some supplemental water during periods of extended drought.

AAES researchers conducted a trial of 323 cultivars from 23 different bedding plant species at the E.V. Smith Research Center in Shorter, during the summer of 1997. Seeds for the trial entries were donated by companies and plants were grown by a nearby commercial transplant producer. Every effort was made to grow the plants using cultural practices that the typical homeowner might use. Raised flower beds were tilled and amended with agricultural limestone and slow-release fertilizer (18-6-12) according to soil test recommendations. After transplanting, the flower beds were mulched with pine bark. No additional fertilizer and no fungicides or insecticides were applied during the season.

All bedding plants were grown in full sun, with the exception of impatiens, which were grown under 60% black shade fabric. Rainfall was supplemented using overhead sprinkler irrigation to provide an equivalent of one inch of water per week. No "deadheading" of spent flowers or other maintenance was performed on any of the plants with the exception of hand weeding.

Plants from each entry were evaluated every two weeks from July 3 through September 29, 1997, using a 0 to 5 scale (0 = plant died; 1 = a small display of foliage with no flowers present; 2 = adequate amount of foliage with one or two flowers present; 3 = sufficient foliage and floral display to be attractive in the landscape; 4 = plants with an above average floral display and sufficient foliage display; and 5 = superior floral display and sufficient foliage display). Flowering plants were rated primarily on their floral displays, while size, shape, and freedom from insect or disease blemishes also were considered. Any plant rated an average of 2.5 or higher could be considered acceptable in the landscape and would be a worthwhile addition to a garden located in temperate zone eight.

Highest overall ratings were received by impatiens and wax begonia, with five impatiens and six wax begonia cultivars appearing in the list of 12 top performing plants (see the table). Many impatiens in the Super Elfin and Dazzler series of cultivars performed well. Wax begonias in the Eureka series also performed well. These plants are tall-growing types of begonia rather than the more common short, rounded form. Ageratum had one cultivar in the top 12 and two others, Royal Hawaii and White Hawaii, received ratings higher than 3.0.

Average Rating for Top 12 Cultivars Grown in the 1997 Summer Trials, E.V. Smith Research Center, Shorter
 Genus species

 Cultivar*

 Flower color

 Avg. rating
Impatiens wallerana Super Elfin Melon Rose 4.1
Begonia x semperflorens Eureka Scarlet Scarlet 4.0
Begonia xsemperflorens Prelude White White 3.9
Begonia x semperflorens Eureka Bronze Rose Rose 3.9
Impatiens wallerana Showstopper Cherry Red 3.9
Ageratum houstonianum Blue Hawaii Blue 3.8
Begonia x semperflorens Stara Deep Rose Rose, dark 3.8
Impatiens wallerana Super Elfin Rose Rose 3.8
Begonia x semperflorens Stara Mixed Mix 3.7
Begonia x semperflorens Stara White White 3.7
Impatiens wallerana Dazzler Deep Orange Orange 3.7
Impatiens wallerana Dazzler Pink Pink 3.7
*Bedding plant cultivars are frequently developed and marketed in a series. Cultivars in a series share common characteristics, such as height, growth habit, or disease resistance, but differ from each other in flower color. The name on the label often begins with the name of the series followed by the flower color (e.g. Carpet Blue).

Annual vinca is noted for its tolerance of hot, dry locations in the landscape. All the annual vinca cultivars in the trial received ratings higher than 2.5 with Pacifica Orchid, Pacifica Punch, and Blue Pearl receiving the three highest ratings.

Three species of cockscomb were evaluated in 1997. Three plume cockscombs (Castle Yellow, Century Red, and Forest Fire) and two spike cockscomb (Flamingo Purple and Flamingo Feather) rated higher than 2.9. However, cultivars of crested cockscomb did not perform well, with ratings less than 2.0. Two other entries that performed well were Swan River daisy and strawflower.

Globe amaranth is an old-fashion annual that is regaining popularity in the Southeast due to its excellent heat tolerance and the development of new cultivars. Three cultivars evaluated in 1997 received ratings higher than 2.8, Woodcreek Red, Woodcreek Lavender, and Woodcreek Rose. Another old-fashion annual, flowering tobacco, had two cultivars receiving acceptable ratings (higher than 2.5), Prelude Rose and Prelude Red.

Zinnias have been grown in the Southeast for more than a century, but are prone to foliar diseases. Two cultivars that rated higher than 3.0 and appeared to be disease resistant were Oklahoma Formula Mix and Blue Point Formula Mix. Though a recent introduction to southern gardens, creeping zinnia is quickly proving its toughness and reliability. Unlike its upright counterpart, creeping zinnia is a low, spreading plant with characteristics similar to a flowering ground cover. Two cultivars rated higher than 2.5 in the 1997 trial, Goldsmith and Star White.

Of the 76 cultivars of petunia in the 1997 trial, only 26 rated 2.5 or higher. Most of these can be found in a variety of flower colors in the Carpet series or the Fantasy series. A new development in petunias for warm climates are the tropical or spreading petunias. Purple Wave and Pink Wave appeared to thrive in the summer heat, rating 3.3 and 3.0, respectively. Portulaca, which has a spreading growth habit, had two cultivars rated 2.5 or higher, Sundial Fuchsia and Sundial Orange.

Gardeners often rely on marigolds as a mainstay of the annual planting. There are two types of marigolds. African marigolds are generally tall with large flowers while French marigolds are more compact with more numerous, but smaller flowers. Eight African marigolds and 17 French marigolds rated 2.5 or higher. The top three of each type were Antigua Primrose, Antigua Goldsmith, and Discovery Yellow of the African type and Bonanza Harmony, Bonanza Flame, and Hero Orange of the French type.

Most gardeners think of red-flowered scarlet sage when annual salvia is mentioned. However, none of the 17 cultivars evaluated in 1997 received ratings higher than 2.0. A better salvia for the Southeast is mealy-cup sage. Two cultivars rated 2.5 or higher, Victoria White and Signum.

The verbena cultivar Imagination was another excellent performer that received a rating of 2.5. This plant can be treated as a perennial in South Alabama. It has a low growing habit with finely dissected leaves and dark purple blooms that lasted into the fall.

Seed companies and retailers are constantly developing new bedding plant cultivars and products. Recently, they have focused their efforts on the growing southern market by developing new bedding plant types and cultivars for warm environments. Ongoing research is needed to evaluate these new products for their performance in the southern landscape.

Detailed information on the results of this study is available in Circular 320, 1997 Summer Trial Garden Results, available from the Office of Research Information, Room 2 Comer Hall, Auburn University, AL 36849.

Kessler is Assistant Professor of Horticulture; Behe is former Professor of Horticulture and now at Michigan State University; and Bannon is Director of the E.V. Smith Research Center in Shorter.


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