1997 Summer Trial Garden Results

The authors gratefully acknowledge the substantial donation of seed from the companies listed in this publication, as well as the time and effort of David and Martha Wright of Wright’s Greenhouse and Nursery, Inc., Plantersville, Alabama, for growing all the transplants used in this study. K-Power generously donated fertilizer for this study.

INTRODUCTION

In the summer of 1997, 323 bedding plant cultivars were evaluated in the All-America Selections (AAS) Display Garden at the E.V. Smith Research Center (EVSRC). The objective of this study was to determine overall performance of summer-flowering annual plant cultivars (bedding plants). Results generated from this study will assist Alabama horticultural professionals and consumers in bedding plant selection. Landscape performance may vary from year to year as climatic conditions affect performance.
AAS is a non-profit organization founded in 1932 to encourage the development of superior flower and vegetable cultivars through controlled trials. Cultivar selection is based on seed company donations and varies from year to year. Selection of AAS “winners” is based on cultivar performance throughout the nationwide trial system. Winners are prominently displayed for professionals and consumers to see in the landscape through a network of display gardens and printed media. The EVSRC Trial Garden was established as an AAS Display Garden in 1993.
EVSRC, a unit of the Alabama Agricultural Experiment Station, is located in Shorter, 26 miles east of Montgomery, Alabama (latitude 32° 30' N, longitude 85° 40’W). Similar tests were conducted at more than 200 display gardens throughout the United States to assess the general performance of new bedding plant cultivars under local environmental conditions. Other display gardens in Alabama are Bellingrath Gardens in Theodore and the Birmingham Botanical Garden. This publication summarizes results from the E.V. Smith trials. Comparison of results from several display sites will increase the reliability of findings because weather, soil type, exposure, cultural practices, and other variables can greatly affect plant performance. Horticulturists are urged to visit several trial gardens to gain a better understanding of cultivar performance throughout a region or market area.

METHODS

Seeds for the trial entries were donated by several companies and grown by a nearby commercial transplant producer. Raised beds of Norfolk-Orangeburg loamy sand association soil (fine, loamy, siliceous, thermic Typic Kandiudults) were tilled and fumigated with methyl bromide two weeks before planting. No other fungicides or insecticides were applied during the trial period. A commercially available slow-release fertilizer (18-6-12) was pre-plant incorporated into the beds based on soil test recommendations. No additional fertilizer was applied during the season. Transplants were planted on May 27, 1997. Twelve plants per entry were grown in full sun, with the exception of impatiens, which were grown under aluminum hoop frames covered with 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.
Eight of 12 plants (two rows of six plants) per entry were evaluated every two weeks from July 3 through September 29, 1997. The four plants on each end of the two rows were not evaluated. Plants were rated by the same individual using a 0 to 5 scale. Flowering plants were rated primarily on their floral displays, while size, shape, and freedom from insect or disease blemishes were also considered. A rating of 0 indicated the plant had 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—above average floral display and sufficient foliage display; and 5—superior floral display and sufficient foliage display. Ratings were made in whole number units. Any plant rated 2.5 or higher could be acceptable in the landscape and would be a worthwhile addition to a garden located in temperate zone eight.

CLIMATIC CONDITIONS

In 1997, average daily air temperatures were higher than average temperatures for the last 30 years (Table 1). Average monthly rainfall was higher in June, but lower in July, August, and September than average rainfall for the last 30 years. In general, it was dryer than normal during the evaluation period in 1997. Figure 1 shows the minimum and maximum daily air temperatures for 1997.

TRIAL HIGHLIGHTS

The highest overall rating for any plant this year was Impatiens wallerana ‘Super Elfin Melon’ with a rating of 4.1.
Begonia × semperflorens ‘Eureka Scarlet’ came in second with a rating of 4.0. ‘Eureka Scarlet’ is an upright, tall-growing type of begonia as opposed to the short, rounded form of the more popular varieties.
Begonia × semperflorens ‘Prelude White’ and ‘Eureka Bronze Rose’ and Impatiens wallerana ‘Showstopper Cherry’ tied for third with a rating of 3.9. Begonia × semperflorens ‘Encore Pink’, Catharanthus roseus ‘Pacifica Orchid’, Impatiens wallerana ‘Accent Salmon’ and ‘Pride Salmon Orange’, and Zinnia elegans ‘Oklahoma Formula Mix’ were ranked seventh at 3.5.
Eighth place performers were begonia ‘Encore White/Bronze’ and ‘Stara Pink’; impatiens ‘Dazzler Cranberry’, ‘Accent Pastel Mixture’, ‘Bruno Orange’, ‘Accent Mystic Mix’, ‘Accent Deep Pink’, ‘Mosaic Rose’, and ‘Super Elfin Lipstick’; and petunia ‘Carpet Pink’, ‘Carpet Salmon’, and ‘Carpet Rose’ with a rating of 3.4.
Ninth place winners rated 3.3. These included Ageratum houstonianum ‘Royal Hawaii’; Begonia × semperflorens ‘Super Olympia Red’, ‘Eureka Rose’, and ‘Prelude Rose’; Catharanthus roseus ‘Pacifica Punch’; Celosia plumosa ‘Castle Yellow’; Celosia spicata ‘Flamingo Purple’; Gomphrena globosa ‘Woodcreek Red’; and Petunia ‘Pink Wave’. The best performers in tenth place were Begonia × semperflorens ‘Vodka’ and ‘Partyfun Mix’, Impatiens wallerana ‘Pink Swirl’ and ‘Accent Peppermint Mix’, Petunia × hybrida ‘Carpet Velvet’ and ‘Carpet Lilac’, and Tagetes patula ‘Bonanza Harmony’, all rated 3.2.
The Salvia farinacea varieties—‘Victoria White’, ‘Signum’, ‘Reference’, ‘Strata’, and ‘Rhea’, rated 3.1, 2.5, 2.5, 2.4,and 2.3, respectively—performed better than all but two of the Salvia splendens varieties—‘Salsa Scarlet’ (2.2) and ‘Salsa Light Purple’ (2.1). Tagetes erecta ‘Antigua Primrose’ was the best performing African marigold (2.9) while Verbena × speciosa ‘Imagination’ was the best performing verbena (2.5).
Table 2, on pages 5-13, presents the average rating for all flowers grown in the 1997 summer trial garden. Flowers are arranged by genus and species, color, source, and rating. Photographs on pages 14-17 illustrate many of the top-performing plants. Figures on pages 18-25 plot the ratings of selected cultivars throughout the growing season.

EVALUATOR'S NOTES

The tall begonia cultivars, which were added in large numbers to the trial gardens this year, were particularly notable with a tall, open growth habit and profuse blooms. They could be exceptionally attractive in the landscape in either bright shade or part sun, and are available in a wide selection of leaf and flower colors. If marketed properly, they could become very popular.
Among the preferred selections this year were Petunia × hybrida ‘Pink Wave’ and ‘Purple Wave’. They are the best large-flowered petunias for this area, lasting through hot humid summers like no other petunia. The multiflora petunias are a small-flowered form with many blooms covering short compact plants that also performed very well.
Verbena speciosa ‘Imagination’ is another excellent performing summer annual that can be treated as a perennial in this area. It has a low-growing habit with finely dissected leaves and dark purple blooms which lasted into the fall. Normally, the tall growing zinnias are unsatisfactory because they tend to get powdery mildew. However, Zinnia elegans ‘Oklahoma Formula Mix’ was particularly attractive as was Zinnia elegans ‘Big Red’ last year (not included in the trial this year). Thread-leaf zinnias, Zinnia angustifolia ‘Gold’, ‘Star White’, ‘Star Orange’, and ‘Crystal White’, continue to be favorites. They are hardy plants that will take full sun, some drought, and have excellent landscape potential for the front of a border where they will bloom the entire summer until the first frost. However, they require warm weather for best performance.

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