In 2010, both the rhododendron and mountain laurel collections at the Jenkins Arboretum became nationally recognized by the American Public Gardens Association and joined its Plant Collections Network (formerly North American Plant Collections Consortium, NAPCC) – a group of botanical institutions dedicated to preserving plant germplasm.
Since its inception in 1976, Jenkins Arboretum & Gardens has built a remarkable collection of ericaceous plants. With over 4000 accessions representing over 1300 taxa, the Rhododendron/azalea collection at Jenkins is the most noteworthy. It is also incredibly diverse with all five major divisions within the genus are represented – lepidote rhododendrons (those with scaly leaves), elepidote rhododendrons (those with non-scaly leaves), evergreen azaleas (all from Asia), deciduous azaleas (mainly eastern US natives) and even vireya rhododendrons (mostly tropical epiphytes). The collection includes all species of eastern US native azaleas.
In addition to rhododendrons and azaleas, the Arboretum has amassed a fine collection of Kalmias, or laurels. Of the seven Kalmia species native to North America, climate limits the Jenkins collection to only K. latifolia, mountain laurel, and its thin-leaved cousin K. angustifolia, sheep laurel. It is interesting to note that these are the only two species native to this region of Pennsylvania.
While the Arboretum’s Kalmia collection is significantly smaller than its Rhododendron collection, it is still quite diverse with nearly 300 accessioned plants representing 43 taxa. The mountain laurels are most prominent with 40 cultivars on display and dozens of specimens growing wild on the rocky hillside.
The success of these collections is a result of moist, well-drained, acidic soils and ample rainfall during the growing season. Perhaps the main factor however, is simply the location of the Arboretum. Being situated on the edge of zones 6b and 7 and having both north and south-facing slopes, Jenkins is able to display both evergreen azaleas, which grow best further south, and large leaf rhododendrons, which grow best further north.
Currently, Jenkins is working on preservation and collections expansion to include some of the best new cultivars from east coast hybridizers as well as known-provenance deciduous native species.