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Submitted to: Journal of the Magnolia Society International
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/21/2011 Publication Date: 12/1/2011 Citation: Fare, D.C. 2011. A Comprehensive Evaluation of Yellow-flowering Magnolias. The Journal of the Magnolia Society International. 90:13-29. Interpretive Summary: A collection of yellow-flowering magnolias were evaluated for flower color and bloom duration as well as growth rate in USDA Hardiness Zone 6b. The darkest yellow tepals were on Judy Zuk and Yellow Bird. Butterflies and Elizabeth were the earliest to bloom and Elizabeth had the longest flowering period. Goldfinch, Gold Star and Banana Split had the greatest height growth and Golden Sun had the least. Powdery mildew, a foliar leaf pathogen, was greatest on Daybreak, Eva Marie, Golden Gala, Golden Sun, Solar Flair, Stellar Acclaim, Sun Burst, Sunsation and Yellow Bird. Two popular selections in the nursery trade, Butterflies and Elizabeth, had the least amount of powdery mildew. Bud incompatibility with the root system was prevalent which resulted in plant death or disfigured the trunk with swollen tissue above or below the bud union. Further research is needed to identify the most compatible root stock for deciduous magnolia hybrids. Technical Abstract: A collection of yellow-flowering magnolias were evaluated for flower color, bloom duration and growth rate in USDA Hardiness Zone 6b. All selections were reported to have yellow blooms; however, tepal color in this test ranged from light pink with some yellow coloration to dark yellow. The darkest yellow tepals were on Judy Zuk and Yellow Bird. Butterflies and Elizabeth were the earliest to bloom and Elizabeth had the longest flowering period. Goldfinch, Gold Star and Banana Split had the greatest average height growth, 114, 99 and 97 cm, respectively, in comparison to Golden Sun with 22 cm. Trunk growth averaged from 9 mm to 29 mm during the test. Carlos, Yellow Lantern, Sundance, Gold Star and Golden Gala had the most trunk diameter increase and averaged over 25 mm (one inch) growth per year. Golden Gift, Daybreak, Golden Sun and had the least trunk diameter growth increase with yearly averages of 9, 11 and 12 mm, respectively. Powdery mildew, Erysiphe magnifica, was greatest on Daybreak, Eva Marie, Golden Gala, Golden Sun, Solar Flair, Stellar Acclaim, Sun Burst, Sunsation and Yellow Bird with 40 percent of the leaf area affected and over 60 percent of all the leaves affected. Two popular selections in the nursery trade, Butterflies and Elizabeth, had the least amount of powdery mildew and were similar to Sun Spire and Carlos. Bud incompatibility with the root system was prevalent which resulted in plant death or disfigured the trunk with swollen tissue above or below the bud union. Further research is needed to identify the most compatible root stock for deciduous magnolia hybrids. |
