Arboriculture & Urban Forestry 33(2): March 2007 Arboriculture & Urban Forestry 2007. 33(2):153–156. 153 Callery Pear Cultivars Tested As Street Trees: Final Report on a 12-year Study Henry D. Gerhold Abstract. Cooperators in the Municipal Tree Restoration Program planted nine Callery pear (Pyrus calleryana Decne.) cultivars in 11 Pennsylvania, U.S. communities for evaluation as street trees, comparing two cultivars (three in one case) in each community. Cooperators measured them annually with standardized methods for 3 years and then at 3-year intervals until the 12th year. The most noteworthy differences occurred in tree height and crown width. The tallest were Aristocrat™, ‘Cleveland Select’, and ‘Redspire’, attaining more than 8 m (26 ft) on average by the twelfth year and even 10.3 m (34 ft) in one community. ‘Autumn Blaze’, evaluated only at one location, was ≈1.5to2m(5to6.6ft) shorter in the 12th year. Heights of the other cultivars, tested at just one or two locations, were similar to the tallest ones. Crown widths differed more in the first 9 years than at the twelfth when on average most were ≈6.5 m (21.5 ft) wide. Cleveland Pride® Select’, Valiant® , and ‘Whitehouse’ were narrower than the others until the ninth year, but only ‘Cleveland Select’ at ≈5.6 m (18.5 ft) remained narrower in the twelfth year and not everywhere. All cultivars were in good health during the whole period, although the foliage of ‘Whitehouse’ exhibited minor injuries in many years. As street trees, the Callery pears were not invasive and did not yet experience branch breakage, which can become a serious problem. All of the cultivars are too tall to be planted under utility wires. Key Words. Callery pear cultivars; performance testing; Pyrus calleryana; street tree evaluation. , ‘Cleveland This final report brings to a conclusion a series of evaluations of nine Callery pear (Pyrus calleryana) cultivars planted in Pennsylvania, U.S. as street trees. Two previous reports (Ger- hold and McElroy 1994; Gerhold 2000) provided preliminary data up to 9 years after planting, and results have now been extended to the twelfth year. Performance test plantings of the Municipal Tree Restoration Program (MTRP), which in- clude many more species and localities, have encouraged municipalities to improve their tree programs. The test plant- ings serve as demonstrations of utility-compatible trees, and results provide information helpful for selecting appropriate cultivars that can be planted under utility wires. Callery pears have been quite popular after introduction of the ‘Bradford’ cultivar in 1963 as a result of their attractive flowers and foliage, and tolerance of urban conditions. Their features as landscape trees have been evaluated in various locations, including Alabama (Fare et al. 1991), New Jersey (Kuser et al. 2001), and Ohio (Haserodt and Sydnor 1983). MATERIALS AND METHODS Plants and Experimental Design Cooperators planted the nine Callery pear cultivars in 11 Pennsylvania communities during 1988 to 1993. Community representatives chose the planting sites with the advice of utility foresters, service foresters in the Bureau of Forestry, or Penn State extension urban foresters. Each test planting in a community consisted of two paired cultivars, except in Tioga where there were three. A typical test consisted of two cultivars planted alternately within 4 to 10 plots that contained 4 to 16 trees each for a total of 50 trees. All test trees were planted along streets and under elec- tric conductors. The utility company arranged for the removal of large trees in the plots that interfered with utility lines, thus making space for planting in some of the plots. Plant Materials The test trees came from several nurseries as balled-and- burlapped stock, and the same nursery always supplied both cultivars for a community. Calipers ranged from 4.4 to 5.1 cm (1.76 to 2 in) and heights from 2.8 to 5.0 m (9.2 to 16.5 ft). The wide range in heights presumably could be explained by genetic differences among cultivars and diverse cultural dif- ferences among nurseries that supplied the trees. ‘Redspire’ typically was 0.2 to 0.6 m (0.7 to 2 ft) taller than its com- panion cultivar; ‘Cleveland Select’ planting stock tended to be shorter but not in all cases. No unusual climatic events occurred during the study. Wet snow or ice before leaf-fall can cause devastating branch ©2007 International Society of Arboriculture
March 2007
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