| HWA
preferences, nonnative hemlock hardiness |
Paul
Jost |
| Jan
25, 2007 19:32 PST |
Has anyone seen Hemlock Woolly Adelgid in an area where both the
native
eastern or Carolina hemlocks coexist with non-native hemlocks
such as
western hemlock, mountain hemlock, northern or southern Japanese
hemlocks, or any of the mainland Asian hemlocks? I am curious
about
whether or not adelgids show a preference where hemlock species
coexist.
Of the nonnatives, interior origin western hemlocks (Tsuga
heterophylla), and northern Japanese hemlocks (Tsuga
diversifolia) stand
any chance of growing in northern parts of the eastern hemlock
range.
The USFS silvics manual claims that western hemlock whose range
includes
Alberta, Canada as well as northern Idaho and Montana, can
survive
temperatures to -54F, so I assume that this extreme cold
survival is for
interior seed sources only. The northern Japanese hemlock is
reported by
the USFS to survive to below -63F. Does anyone know of
successful far
northern plantings of these species in the east?
As the adelgid spreads, I am becoming more concerned about the
small
hemlock grove that I own in northern Wisconsin. I am considering
experimental plantings of the cold hardy nonnatives in advance
of native
hemlock loss. I can find low cost seed and seedling sources for
northern interior western hemlock, but hundreds quantity low
cost
northern Japanese hemlock is a problem. Does anyone have any
sources?
Paul Jost |
| RE:
HWA preferences, nonnative hemlock hardiness |
Steve
Galehouse |
| Jan
25, 2007 19:56 PST |
Paul-
I have growing in my yard, in N Ohio, Tsuga mertensiana cv. Mt.
Hood,
perfectly hardy but very slow growing(5' tall after 10+ years)
and
"un-hemlocky" in appearance, with blue-green needles
reminiscent of
Cedrus atlantica glauca. The Asian species are obscure at best
from a
horticultural viewpoint, with T. diversifolia resembling
Carolina
hemlock more than eastern hemlock.
The adelgid has not invaded our area yet, so no comment on
resistance.
|
| Re:
HWA preferences, nonnative hemlock hardiness |
orw-@fas.harvard.edu |
| Jan
26, 2007 06:54 PST |
Paul, I can tell you I've seen Tsuga canadensis covered with HWA
less
than 1 m from a Tsuga chinensis (same size) without a single
adelgid!!!
They clearly and very definitely show a preference for T.
canadensis and
T. caroliniana (which was also in this same forest, at the
Arnold
Arboretum.). Hope this helps.
Peter del Tredici (along with Alice Kitajima) has written about
this in
a paper 'Introduction and cultivation of chinese hemlock (Tsuga
chinensis) and its resistance to hemlock woolly adeldid (Adelges
tsugae)" Journal of Arboriculture 30: 282-286.2004. hope
this helps
DAVE ORWIG
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