Arboriculture & Urban Forestry 42(5): September 2016 tance, such as HWA (Montgomery et al. 2009; Weston and Harper 2009), elongate hemlock scale (Fiorinia externa Ferris) (EHS) (Hoover et al. 2009; Harper and Cowles 2013), and spruce spider mite (Oligonychus ununguis Jacobi) (SSM) (Del Tredici and Kitajima 2004), may be lim- ited or unavailable. Furthermore, when a speci- men of Tsuga spp. has demonstrated resistance to a pest of importance like HWA (Bentz et al. 2002; Havill and Montgomery 2008), resistance mechanisms, though perhaps suspected to be mechanical or chemical in nature (Oten et al. 2010), may not actually be known (Bentz et al. 2002). Propagation techniques for Tsuga spp., especially T. canadensis, have been published (Del Tredici 1985; Jetton 2008), but little research has focused on the propagation of T. chinensis. This study sought to better understand the term survivability and growth perfor- longer mance of seven species of Tsuga originating from western North America and Asia in the northeastern U.S., nearly nine years after they were planted in research plots in Westches- ter County, New York, U.S. Researchers also aimed to document the ability of T. chinen- sis to be propagated from hardwood cuttings in the early stage of vegetative propagation. MATERIALS AND METHODS Research Site Located in Katonah, New York, U.S. (USDA Har- diness Zone 6b), Lasdon Park and Arboretum is a 94 ha public park that hosts various horti- culture research and teaching interests (Anon- ymous 2013). On 30 September 2003, three 347 experimental plots were established within the deer-fenced portion of the property, designated Front Gate, Magnolia Garden, and Hemlock Hedge. Plant Material Tsuga selection consisted of the following sev- en species based on commercial availability: Tsuga canadensis (L.) Carrière (Canadian/ eastern hemlock)—Although a highly valued ornamental tree in the northeastern U.S., its range extends south to Georgia and Alabama and west to Minnesota. Hardy to USDA Zone 3, it is also found growing at its northern range that extends into the central-eastern portion of southern Can- ada. Its response to shearing and tolerance to shade have made it an ideal hedge species, however. Its graceful form and size—the national champion is 47.5 m in height—also make this tree valued as an individual specimen tree or grouped planting (Farrar 1995; Dirr 2011). As HWA has reduced the salability of T. canadensis and its numer- ous cultivars throughout significant portions of the infestation range, horticulture specialists have continued to answer questions from arbor- ists and other horticulture professionals, as well as the general public, about suitable woody orna- mentals that may supplant the landscape niche that this tree has successfully occupied. Specifi- cally, this includes the natural screening benefits from a maintained T. canadensis hedge, serving to divide shaded suburban properties (J. Gior- dano, Cornell University Cooperative Exten- sion, pers. comm.). Numerous published reports have affirmed host susceptibility to HWA (Table 1) and 28 of the original 36 research specimens have persisted at Lasdon Arboretum (Table 2). Table 1. Summary of Tsuga susceptibility to hemlock woolly adelgid (Adelges tsugae). Ratings are: S = susceptible, T = tolerant, R = resistant, ? = questionable. Author(s)/year McClure/1992 del Tredici & Kitajima/2004 Montgomery & Lagalante/2008 Montgomery et al./2009 Weston & Harper/2009 Harper & Weston (current study) Speciesz can S S S S S S car S S S S S S = T. sieboldii. Note: Dashes (---) indicate species that were not evaluated in certain studies. het T ? ? --- S S mer T --- R --- R R div S R R --- R S sie S ? S S R R chi --- R R R R R z Species abbreviations are as follows: can = T. canadensis, car = T. caroliniana, het = T. heterophylla, mer = T. mertensiana, chi = T. chinensis, div = T. diversifolia, sie ©2016 International Society of Arboriculture
September 2016
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
