Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2004
Publication Date: 6/5/2005
Citation: Reed, S. 2005. Japanese snowbell exhibits varibility for time of vegetative budbreak and susceptibility to spring freeze damage. HortScience. 40:542-545. Interpretive Summary: Japanese snowbell (Styrax japonicum) is a small deciduous tree that is cultivated as an ornamental. It grows from 20 to 30 feet in height and width and produces attractive, fragrant flowers in mid-spring. Despite the outstanding attributes of this tree, it is not widely utilized in the U.S. One of the reasons Japanese snowbell is not more widely planted is that it often suffers damage from spring freezes. This study was conducted to determine if there were differences in susceptibility to spring freeze damage between plants of this species. During spring 1999 and 2000, 224 seedlings were evaluated weekly for percentage of buds that had broken dormancy. Data from the two years were compared, and 28 plants that were slow to break dormancy both years were selected for further evaluation. These plants, along with three cultivars, were propagated and planted in a replicated trial where data was collected from 2002 to 2004. All of the selections broke bud later and suffered less freeze damage than 'Emerald Pagoda' and 'Carillon', but many performed similarly to 'Pink Chimes'. Variation in height, width, trunk diameter, and canopy shape was observed among the selections. Plants identified in this study as having reduced susceptibility to spring freeze damage and superior ornamental qualities may eventually be released as new cultivars.
Technical Abstract: Japanese snowbell (Styrax japonicum) is an outstanding small ornamental tree that is underutilized in the U.S. One of the reasons this Asian native is not more widely planted is that it is subject to spring freeze damage. The objectives of this study were to determine if there was variability within S. japonicum for time of budbreak and if this variability could be used for selecting plants better adapted to areas of the country that frequently experience late spring freezes. During Spring 1999 and 2000, budbreak was evaluated weekly in 224 open-pollinated seedlings. While weather conditions varied greatly between the 2 years, there was good consistency between 1999 and 2000 data. There was a 4-week difference between the earliest and latest plants to break dormancy. Based on the 1999 and 2000 data, 28 plants were selected and propagated. A replicated trial involving these selections and three cultivars was carried out in 2002, 2003 and 2004. All of the selections broke bud later and suffered less freeze damage than 'Emerald Pagoda' and 'Carillon', but many performed similarly to 'Pink Chimes'. Variation in height, width, caliper and canopy shape was observed among the selections. There is an opportunity to utilize the genetic variability in S. japonicum for developing cultivars with reduced susceptibility to spring freeze damage.