A new hemlock hybrid has been developed by the Agricultural Research Service (ARS).
The first of its kind hemlock variety is called Traveler. It is a cross between the Chinese hemlock (Tsuga chinensis) and the native Carolina hemlock (Tsuga caroliniana).
Traveler has the native hemlock’s handsome symmetrical evergreen growth habit with slightly weeping branches, moderately slow growth rate and produces large cones.
The most important characteristic of the tree is the ability to survive an attack from the hemlock woolly adelgid.
ARS horticulturist Susan Bentz stated, “We’ve had trials of Traveler growing since 2000, and we haven’t seen any damage from the insects despite the trees being planted out among susceptible Carolina and eastern hemlocks.”
Sap-sucking hemlock woolly adelgids are closely related to the aphid. Originally from Asia, the hemlock woolly adelgid arrived in the United States in 1951 and has since spread to 17 states from Georgia to New England and southwestern Nova Scotia, decimating stands of both Carolina and eastern hemlocks.
The insect has virtually eliminated hemlocks as a marketable ornamental tree in the eastern U.S.
While developing these hybrids, Bentz and her colleagues found that the eastern hemlock (Tsuga canadensis) would not cross with the Chinese hemlock. On the other hand, the Carolina and Chinese hemlock produced several offspring that were verified using molecular techniques.
After promising replicated field and greenhouse trials in Beltsville, MD, the researchers moved on to field trials of Traveler and other similar crosses in North Carolina and Connecticut.
“After 6 years in the North Carolina trial, the average height of Traveler trees planted was 3.5 meters (11.5 feet) and all have survived,” Bentz said. “It will make a very attractive specimen tree in a large yard, park, commercial site or as an informal large screen.”