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2014 - 2017 Azalea Evaluation Program

Azaleas are one of the largest single crops grown by nursery producers in the southeast, generating over $4 million USD in sales in Georgia and 39.5 million USD in sales across six southeastern states Census of Agriculture, 2007. Being the largest flowering woody ornamental crop group grown in the southeast, maximizing flowering potential and plant production is extremely important to the profitability of commercial growers. New plant introduction and integration into production systems continues to be a challenge for growers due to the sometimes overwhelming number of cultivars available on the market. The requirements of the market compound these challenges due to the short sales window that is often influenced by spring weather/climate. In recent years, the market for azaleas has been transformed with the introduction of a plethora of new cultivars, bringing a new interest in this specialty crop. There are now 66 cultivars of re-blooming azaleas available along with over 100 commonly available traditional spring only blooming cultivars. This increase in cultivars and the challenges of the marketplace have created a need for better information. Due to the nature of the nursery industry, producing and publishing information based on their own observations, reliable standardized information of cultivar characteristics is not available. This study was designed to address three primary needs; (1) to develop information needed for producers and consumers/end users to be able to evaluate and choose the best cultivar(s) to meet their needs, (2) to identify pest-resistant cultivars that will thrive in landscape environments, and (3) to find ways to manipulate the bloom period of azaleas in order to speed or delay flowering to coincide with the desired market window.

The objective of the project was to allow CANR to address the aforementioned needs. The first of these needs, to develop the information needed for growers, retailers, landscape contractors, and consumers/end users to be able to evaluate and chose the best azalea cultivars to meet their needs, was approached using several techniques. CANR secured and trialed 150 cultivars of azaleas at CANR, representing re-blooming azaleas and the most common commercially available traditional spring-only flowering azaleas. These cultivars were evaluated for timing of flower, flower size, and color under the same environmental conditions, to develop a true comparison of flowering period. Longer term growth habit and cold hardiness for each cultivar was researched from external authoritative sources. This information will allow professionals and consumers to make informed choices on which cultivar(s) fits their needs. The project also provided for the evaluation and identification of cultivars with lower levels of azalea lace bug and strawberry root weevil damage, therefore requiring less intensive pest management and therefore a greater profitability for the producer and more environmentally friendly option for the consumer. The project allowed CANR to consolidate this information into easy to understand publications that are available in a digital format free for download and use from the CANR website. Additionally, posters have been printed and will be distributed at meetings of the Green Industry for use by professionals to increase the visibility of this information to the consumer.

The last objective of the project was to determine methods to manipulate the bloom period of azaleas in order to speed or delay flowering to coincide with the desired market window (thereby increasing demand and profitability to producers). In order to accomplish this goal, CANR ran a series of trials to look at dormancy and chemical plant growth regulator (PGR) manipulation of flower timing. CANR performed a replicated study looking at the interaction of temperature in the root zone and air temperature and their effect on plant growth and flowering. The information from this study has allowed a better understanding of what environmental factors cause plant growth and flowering. Additionally, CANR ran a series of trials using available PGRs to determine their effect on flowering and growth in an outdoor setting in order to determine the potential to use PGR treatments to modify the timing of flowering. PGR trials were not successful in manipulating peak bloom period for a specific sales window. There was still valuable information gained form this project, including a better understanding of dormancy in azaleas and the interaction of available PGRs on dormancy in azaleas. The information learned via this project will also help in developing potential methods for bloom period modification in other crops in the future. Dr. Chappell (University of Georgia, Horticulture Department) is currently working on the publication of the results from the temperature modification trial in horticultural journals, and a discussion of results from both trials can also be found here the CANR website.

Few intereesting items from the data:

Largest flower size: 
George L. Taber
Mrs. G.G. Gerbing
Tama No Hada
Formosa Purple

Least Amount of Damage from of Azalea Lace Bug: 
Red Slipper
BNA Lavender Twist
Mother's Day
Girard's Hot Shot
Girard's Crimson
Deja Bloom Pink Ribbons
Encore Autumn Fire

Least Amount of Damage from Strawberry Root Worm: 
Flame Creeper
Momo No Haru
Gumpo Pink
The Robe

  Azalea Trial Bloom Photos Poster PDF

  Azalea Cultivar Data Summary Poster PDF

Azalea FlowerAzalea Flower 



 Azalea Bloom Time Environmental Responce PDF

Azalea FlowerAzalea Flower 

 Azalea Plant Growth Regulator Bloom Time Modification Discussion PDF

Azalea Temp Trial

For more information on this project please fee free to contact us email at director@canr.org.

Funding for this publication was made possible by the U.S. Department of Agriculture’s (USDA) Agricultural Marketing Service and the Georgia Department of Agriculture (GDA) through a Specialty Crop Block Grant. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the USDA or GDA.

hydrangea trail