130 according to the percentage injured using a five-point scale: 1 65 to 100, 2 45 to 60, 3 25 to 40, 4 5 to 20, and 5 less than 5. The scale for trunk injuries was 1tree dead, 2 severe injuries, 3moderate, 4slight, and 5no injuries. Causes of injuries such as diseases, insects, drought, or mechani- cal damage were identified when possible and recorded. An analysis of variance (using MINITAB’s [State College, PA] general linear model) of quantitative data collected in a given year calculated means and determined statistical differ- ences between the cultivars and among plots in each community at the 5% level of probability. Each test location in every year constituted a separate experiment with plots providing replica- tion within a community. These results, along with comments provided by cooperators, were used to characterize performance of the cultivars. RESULTS AND DISCUSSION Survival rates were best at Genesee, being 100% for both culti- vars through year 12; also at Laporte, at 100% when last mea- sured in year nine; and at Meadville, where only one tree had been lost through the ninth year. There were wide tree lawns at all of these three locations. At most other locations, survival started declining in the first 3 years, commonly being reduced to 60% to 88% in year 12 and even to 48% in the worst case. At Delaware Water Gap, one-third of the trees had to be replaced after the first year because roots had been pruned excessively when the trees were lifted at the nursery. Investigation revealed that the tree spade had not been centered over the root systems, which were not symmetric. Despite the mortality rates, the ser- viceberries proved to be rather resilient even in downtown situ- ations. For example, survival of the two cultivars was 73% and 80% in Bedford, where nearly all plots had just 0.6 to 0.9 m (2 to 3 ft) between the curbs and sidewalks. Health ratings of the foliage (2.8 to 4.7) and branches (3.5 to 5.0) were similar to those of crabapple cultivars (Gerhold 2007). The foliage was injured more than 40% in only four of 31 cases, and in 14 cases, foliage injury was below 20% when evaluated Gerhold: Serviceberry Cultivars as Street Trees late in the growing season. Differences between cultivars in foliage health were significant in only two of 15 comparisons; in both of these, Autumn Brilliance was superior to Cumulus. Injuries to trunks were infrequent and slight for all cultivars. The principal differences among cultivars were in their di- mensions (Table 1). Average 12-year heights of Cumulus (5.5 to 7.3 m [18.2 to 24.1 ft]) and ‘Robin Hill’ (5.5 to 6.8 m [18.2 to 22.4 ft]) at various locations were greater than heights of Tradition (3.7 to 5.3 m [12.2 to 17.5 ft]) and Autumn Bril- liance (3.9 to 5 m [12.9 to 16.5 ft]). Trunk diameters showed similar relationships. Crown widths of Cumulus (3.8 to 4.6 m [12.5 to 15.2 ft]), ‘Robin Hill’ (2.9 to 4.9 m [9.6 to 16.2 ft]), Tradition (3 to 4.5 m [9.9 to 14.9 ft]), and Autumn Brilliance (3.7 to 4.9 m [12.2 to 16.2 ft]) do not exhibit the same pattern, although there were significant differences at four locations. The tests of ‘Cole’s Select’, ‘Princess Diana’, Reflection™, and Spring Glory also are promising, although they have not been tested as extensively. ‘Cole’s Select’ might be the same cultivar as Autumn Brilliance according to the nurseryman where it was grown; no significant differences between these two have been found in the tests so far. ‘Princess Diana’ in the ninth year was also similar to Autumn Brilliance. Reflection compared well with Tradition but had a narrower crown. Spring Glory had smaller dimensions than ‘Reflection’. The fastest growth rates of the four cultivars for which the most extensive data are available illustrate expectations for the future. The greatest 12-year heights attained by the cultivars at various locations (Figure 1) were Cumulus at Genesee (7.3 m [24.1 ft]), ‘Robin Hill’ at Delaware Water Gap (6.8 m [22.4 ft]), Tradition at Warren (5.1 m [16.8 ft]), and Autumn Brilliance at Genesee (5 m [16.5 ft]). Only Cumulus and Autumn Bril- liance are directly comparable being at the same location. The rate of height growth of the two taller cultivars had not slowed down much or at all by the twelfth year and was approaching some overhead electric utility wires. The projected heights of Tradition and Autumn Brilliance would not reach 7 m (23.1 ft) for another 12 years if at all. None of the heights or widths in Figure 1. Serviceberry cultivar heights at various locations: Cumulus at Genesee, ‘Robin Hill’ at Delaware Water Gap, Tradition at Warren, and Autumn Brilliance at Genesee. ©2008 International Society of Arboriculture
March 2008
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