Callery pear cultivars tested as street trees: Final report on a 12-year study

Abstract

Cooperators in the Municipal Tree Restoration Program planted nine Callery pear (Pyrus calleryana Decne.) cultivars in II 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 ≈1.5 to 2 m (5 to 6.6 ft) 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®, 'Cleveland 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. © 2007 International Society of Arboriculture.