Growth, flowering, and powdery mildew related responses of witchhazels in Tennessee

Authors: Alexander, Lisa; BAYSAL-GUREL, FULYA - Tennessee State University; WITCHER, ANTHONY - Tennessee State University

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2019
Publication Date: 8/13/2019
Citation: Alexander, L.W., Baysal-Gurel, F., Witcher, A.L. 2019. Growth, flowering, and powdery mildew related responses of witchhazels in Tennessee. HortTechnology. 29(4):507-515.

Interpretive Summary: Witchhazel (Hamamelis L.) cultivars are now available in an array of forms and flower colors, including several cultivars of native, pollinator friendly varieties. However, little is known about response of witchhazel cultivars to powdery mildew or the growth and flowering responses of witchhazel cultivars in a nursery field production setting. In order to provide growth, flowering, and disease incidence data to nursery growers, a cultivar trial including twenty-three cultivars of witchhazel representing five species was planted in April 2016 in McMinnville, TN. Plant growth, flowering density, length of bloom, and foliar disease incidence were evaluated over three growing seasons between May 2016 and October 2018. Witchhazel recommendations for Tennessee nursery producers based on growth rate, resistance to powdery mildew, and flowering include ‘Sunglow’, common witchhazel, ‘Little Suzie’ common witchhazel (semi-dwarf habit), ‘Wisely Supreme’ Chinese witchhazel and ‘Nina’ hybrid witchhazel. ‘Sunglow’ has the added benefit of rooting well from cuttings, which means that it could be grown as a cultivar on its own roots rather than grafted. Witchhazel cultivars with resistance to powdery mildew but poor growth in this trial may have production potential for Southeastern growers in USDA Hardiness Zone 7 and warmer. Research regarding production timelines and practices is ongoing. These results should aid in the adoption and production of witchhazel by southeastern nursery producers.

Technical Abstract: Witchhazel (Hamamelis L.) cultivars are now available in an array of forms and flower colors, including several cultivars of native, pollinator friendly varieties. However, little is known about response of witchhazel cultivars to powdery mildew or the growth and flowering responses of witchhazel cultivars in a nursery field production setting. In order to provide growth, flowering, and disease incidence data to nursery growers, a cultivar trial including twenty-three cultivars of witchhazel representing five species was planted April 2016 in McMinnville, TN. Plant growth, flowering density, length of bloom, and foliar disease incidence were evaluated over three growing seasons between May 2016 and October 2018. ‘Zuccariniana’ japanese witchhazel (H. japonica Sieb. & Zucc.) and ‘Sunglow’ common witchhazel (H. virginiana L.) showed the greatest height increase during the trial, while ‘Sunglow’ also added the most width during the trial. Cultivars with negative height or width growth included Sweet Sunshine chinese witchhazel (H. mollis Oliv.) and hybrid witchhazels (H. ×intermedia Rehd.) Aphrodite, Twilight, and Barmstedt Gold. Ten of the 23 cultivars experienced winter injury in the form of stem necrosis. Root crown sprouts were observed for all cultivars at least once during the trial. ‘Wisely Supreme’ chinese witchhazel had the longest bloom period followed by ‘Westerstede’ and ‘Twilight’ hybrid witchhazels, while ‘Quasimodo’ vernal witchhazel (H. vernalis Sarg.) had the greatest density of flowers. The hybrid witchhazel cultivars Aphrodite, Nina and Arnold Promise, and the common witchhazel cultivars Green Thumb and Sunglow were resistant to powdery mildew under trial conditions in all three years. ‘Twilight’ and ‘Barmstedt Gold’ hybrid witchhazel, ‘Little Suzie’ common witchhazel, ‘Wisley Supreme’ chinese witchhazel, and ‘Shibamichi Red’ japanese witchhazel were moderately resistant to powdery mildew.