Serviceberry Cultivars Tested as Street Trees: Initial Results

Methods

Ten communities in Pennsylvania and 1 in New York planted the serviceberry trees represented in this report. Community representatives chose the planting sites with assistance of utility foresters, service foresters, and Extension urban foresters; 2 of these usually assisted each community. A typical cultivar performance test consisted of 2 cultivars planted alternately within 4 to 10 plots that could contain 4 to 16 trees each, a total of 50 trees. All test trees were planted along streets and under electric conductors; the utility company arranged for removal of large trees that interfered with utility lines. Both cultivars for a community were ordered B&B from the same nursery, with calipers of 4.5 to 5.1 cm (1.75 to 2 in.); heights ranged from 2.7 to 4.9 m (9 to 16 ft).

The cultivar tests were planted between 1989 and 1996. A trained cooperator inspected and measured the trees annually during the first 3 years, and then at 3-year intervals in most cases. During September or October, a service forester or Extension urban forester used standardized methods to measure tree height, trunk diameter, and crown width, and to classify foliage health, branch health, trunk health, maintenance needs, and overall quality (see scales in Table 1). Causes of damage such as disease, insects, drought, and mechanical injuries also were recorded.

An analysis of variance (MINITAB General Linear Model) was conducted on each type of quantitative data from the 2 cultivars in a community to calculate means and determine significance of differences. Each test location in every year was treated as a separate experiment with plots providing replication. These results, along with written comments of cooperators, were used to characterize performance of the cultivars.

Results

All of the serviceberry cultivars performed well, at least at some locations, but they were more sensitive than other species such as crabapples and Callery pear (Gerhold et al. 1994; Gerhold and McElroy 1994) to urban stresses, caused for example by compacted soils, heavy traffic, and restricted spaces. Foliage health values below 3.5 (more than 20% of foliage injured) indicated adverse site conditions particularly at Delaware Water Gap, Reading, and Union City (Table 1). Survival rates also suffered at some locations, but mainly for other reasons such as improper planting, vehicle accidents, and vandalism. Nearly half of the cultivar survival percentages within communities were below 80.

Most of the serviceberry cultivars did not differ significantly and consistently from the others, with a single exception. ‘Autumn Brilliance’ in several comparisons was not as tall, had a broader crown, and had healthier foliage. The average percentage survival of ‘Autumn Brilliance’ at 6 locations, including 2 stressful ones, was 97%, whereas the survival percentage of ‘Cumulus’, ‘Robin Hili’, and Tradition® averaged 79, 76, and 75 respectively.

Growth rates differed substantially among locations, and there were inconsistencies between cultivars. For example, ‘Cumulus’ grew faster than ‘Robin Hill’ at Bedford, but the reverse was true at Orrstown (Figure 1). At Union City, the patterns of height growth of ‘Autumn Brilliance’ and Tradition® were similar, even though the latter was taller (Figure 2). However at Warren, Tradition grew little from year 3 to year 6, whereas the height of ‘Autumn Brilliance’ increased more than 1.2 m (4 ft). The reasons for these growth differences are unknown.

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Figure 1.

Height growth of ‘Cumulus’ (Cu) and ‘Robin Hill’ (RH) serviceberry cultivars at Orrstown (Test 16) and Bedford (Test 34).

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Figure 2.

Height growth of ‘Autumn Brilliance’ (AB) and Tradition® (Tr) serviceberry cultivars at Warren (Test 43) and Union City (Test 57).

There were few significant differences among branch health, trunk health, and maintenance needs (not shown). They were caused mainly by mechanical damage and transplant shock. Overall ratings also were variable, inconsistent, and generally differed by less than 1.0, except at Genesee where ‘Autumn Brilliance’ was consistently rated above ‘Cumulus’.

Conclusions

All of the serviceberry cultivars performed reasonably well as street trees, but they were sensitive to the more stressful sites. Therefore, compacted soils, streets with heavy traffic, and restricted space for root development should be avoided. ‘Autumn Brilliance’, ‘Cumulus’, ‘Robin Hill’, and Tradition® all were tested for 6 to 8 years at 4 to 8 locations, indicating results can be used with confidence. ‘Princess Diana’ was planted only in 1 community but appears promising after 3 years. ‘Autumn Brilliance’ was broader, not as tall, had somewhat healthier foliage, and had higher survival after transplanting than the others. All had pleasing characteristics, along with single trunks and branching habits conducive to clearance for pedestrians and vehicles.