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ARS Home » Northeast Area » Washington, D.C. » National Arboretum » Floral and Nursery Plants Research » Research » Publications at this Location » Publication #398582
Research Project: Evaluation and Genetic Improvement of Woody Ornamental Landscape Plants

Location: Floral and Nursery Plants Research

Title: Tsuga ‘Traveler’ and ‘Crossroad’ – the first adelgid-resistant interspecific hemlock hybrids

Author
item Bentz, Susan
item Gouker, Fred
item Olsen, Richard
item Pooler, Margaret

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2022
Publication Date: 1/27/2023
Citation: Bentz, S.E., Gouker, F.E., Olsen, R.T., Pooler, M.R. 2023. Tsuga ‘Traveler’ and ‘Crossroad’ – the first adelgid-resistant interspecific hemlock hybrids. HortScience. 58(3):289–290. https://doi.org/10.21273/HORTSCI16918-22.
DOI: https://doi.org/10.21273/HORTSCI16918-22

Interpretive Summary: Hemlocks are foundational evergreen trees in forested ecosystems and are also iconic in cultivated landscapes. In the U.S., the eastern hemlock is the most well-known and economically significant species for forest and cultivated landscapes. However, this species, along with the Carolina hemlock is highly susceptible to feeding damage by the introduced hemlock woolly adelgid (HWA). While the insect can be controlled using a combination of cultural practices, insecticides, and biological control methods, the most effective long-term control strategy is likely to be host resistance. ARS scientists at the U.S. National Arboretum initiated a breeding program in the 1990s to develop new hemlock hybrids with improved resistance to HWA and superior ornamental traits. They selected, evaluated, and released two of these hybrids, ‘Traveler’, and ‘Crossroad’, for their improved resistance to hemlock woolly adelgid and outstanding ornamental and growth characteristics. These are the first interspecific hybrid hemlocks to be introduced to the horticultural trade, and represent new strategies for managing HWA in landscape settings.

Technical Abstract: Hemlocks (Tsuga species) are foundational, climax coniferous evergreen trees in forested ecosystems and are also iconic in cultivated landscapes. In the U.S., the eastern hemlock, T. canadensis, is the most well-known and economically significant species for forest and cultivated landscapes. However, this species, along with the Carolina hemlock, T. caroliniana, is highly susceptible to feeding damage by the introduced hemlock woolly adelgid (HWA), Adelges tsugae. Scientists at the U.S. National Arboretum initiated a breeding program in the 1990s to develop new hemlock hybrids with improved resistance to HWA and superior ornamental traits. Breeding strategies are focused on interspecific hybridizations to incorporate HWA resistance found in Asian Tsuga species T. chinensis, T. diversifolia, and T. sieboldii. These crosses resulted in over 100 confirmed interspecific hybrid plants. We have selected, evaluated, and released two of these hybrids, T. chinensis × T. caroliniana ‘Traveler’, and T. caroliniana × T. chinensis ‘Crossroad’, for their improved resistance to hemlock woolly adelgid and outstanding ornamental and growth characteristics. These are the first interspecific hybrid hemlocks to be introduced to the horticultural trade, and represent new strategies for managing HWA in landscape settings.