154 Gerhold: Callery Pear Cultivars As Street Trees breakage in this species, but none was reported at any of the study sites. Measurements and Analysis A trained cooperator inspected and measured the trees soon after planting, then annually during the first 3 years, and at 3-year intervals afterward. During September or October, a service forester or extension urban forester, using standard- ized procedures, measured tree height, trunk diameter, and crown width; classified the health of foliage, branches, and trunk separately; and rated maintenance needs and overall quality. The health of foliage and branches was estimated according to the percentage injured using a 5-point scale: 1 65 to 100, 245 to 60, 325 to 40, 45 to 20, 5<5. The scale for trunk injuries was 1 tree dead, 2 severe injuries, 3 moderate, 4 slight, 5 no injuries. Causes of injuries such as by diseases, insects, drought, or mechani- cal damage were identified and recorded when possible. An analysis of variance (using MINITAB’s General Linear Model) of quantitative data collected in a given year calcu- lated means and determined statistical differences between . cultivars at the 5% level of probability. Each test location in every year constituted a separate experiment with plots pro- viding replication within a community. These results, along with comments provided by cooperators, were used to char- acterize performance of the cultivars. RESULTS The most extensive information was obtained for Aristocrat (in four communities), ‘Cleveland Select’ (in seven), and ‘Redspire’ (in four) (Table 1). These three cultivars turned out to be the tallest after the third year (Figure 1); their average heights in the 12th year were ≈8.5m(28 ft). ‘Autumn Blaze’ at 6.7 m (22 ft) was the shortest, although evaluated in only one community, where it was 1.2 m (4 ft) shorter than ‘Redspire’. The other cultivars, evaluated in one or two com- munities, were in most cases similar in height or not quite as tall as the largest cultivars. The average crown widths of some cultivars differed by ≈2 m (6.6 ft) through the sixth year (Figure 2), but most con- verged at ≈6 to 7 m (19.8 to 23 ft) in the 12th year (Table 1). ‘Cleveland Select’ was narrower, most commonly between 5 Table 1. Size and health ratings of Callery pear cultivars, planted as street trees, two or three cultivars paired in each communityz Cultivar/abbreviation Aristocrat™/Ar ‘Autumn Blaze’/AB ‘Bradford’/Br ‘Capital’/Ca Cleveland Pride® /CP ‘Cleveland Select’/CS Paired cultivar Rd CS, Rd CS CS Rd Wh CS CS Wh ‘Redspire’/Rd ‘Whitehouse’/Wh Valiant® /Va Ar, Rd Ar Ca Va Ar CP AB Ar, CS Ar Va CS Br CS Rd Year 12 12 12 12 12 12 10 12 12 12 12 11 10 12 12 12 12 12 12 12 12 10 12 Diam. (cm) 22.8y 23.3y 24.1 21.6 18.6 23.3y 20.9y 17.4 17.6 15.6x 24.1 14.4x 12.4 20.3 17.3 18.5 19.8y 15.1x 16.2y 18.1 19.4x 12.7 14.1x Ht. (m) 8.68 10.30 7.65 8.35 6.65x 8.84 6.97y 6.97x 8.78y 10.00 7.65 6.10x 6.06 8.32 7.53y 7.84y 9.45 8.38 8.16y 8.08x 8.54 6.00 7.31x Width (m) 6.00 7.29 6.88 5.91y 7.37 7.71y 6.46 6.64y 5.49 6.34 6.88 5.45 5.15 5.12x 4.87x 7.89 7.13 5.66 4.81x 5.51 6.43x 5.58 6.34y Foliage (1 to 5) 4.9 4.3 4.1 4.1 4.7 4.6y 4.9 4.9 4.7y 4.5 4.3 4.8 4.7 4.2 5.0 4.6 4.5 4.8 4.7 3.8x 3.5x 4.7 4.3 Branches (1 to 5) 4.8 4.5 4.5 4.7 4.3 4.5 4.7 5.0 4.6 4.7 4.5 4.5 4.9 4.8 5.0 4.2 4.6 4.7 4.9 4.0 4.1 4.8 4.8 zAverage trunk diameter, tree height, and crown width are in the most advanced year; foliage health and branch health ratings are averaged over all years: 1, 2, 3, 6, 9, and 12 in most cases. ySignificantly greater at 95% level than corresponding value of the paired cultivar. xSignificantly smaller at 95% level than corresponding value of the paired cultivar. Foliage and branch health ratings: 165% to 100% of leaves or branches exhibit injury, 2 45% to 60%, 3 25% to 40%, 4 5% to 20%, 5 less than 5%. ©2007 International Society of Arboriculture
March 2007
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