University of Vermont Extension
Department of Plant and Soil Science
ASH TREE ALTERNATIVES
Dr. Leonard Perry, Extension
University of Vermont
Some of the better native trees in our home and city
landscape plantings are ashes, available in several species and cultivars
(cultivated varieties). Most common are
the white ash (Fraxinus americana),
rounded up to 60 feet tall when mature, and the green ash (Fraxinus pennsylvanica), oval to upright reaching 60 feet
tall. Both have a moderate to fast
growth rate, with yellowish fall leaves.
trees also are valuable for their timber which, being tough, is used for tool
handles and sports equipment. Unfortunately,
a new invasive and exotic pest—the emerald ash borer— threatens these in the
Midwest and mid-Atlantic states, and is slowly spreading towards and into New
England. Since trees affected with this
borer lose half their leaves in 2 years and often die within 4 years, it may be
wise to plant trees other than ash. Or,
if you have ash trees, you may want to have others growing near them.
though this pest is not yet through most of our region or in Vermont, many
experts think it will appear soon since it is in southern New England, New York
state, and Quebec. The purple rectangles
you may see hanging along roads from trees are monitoring traps for this
pest. This introduced pest was first spotted in
southeastern Michigan near Detroit in 2002, likely coming into our country from
Asia on wooden packing materials. A
study was begun in 2003 by Dr. Bert Cregg and others at Michigan State
University, near the epicenter of the original outbreak, on suitable
alternative trees to the ash.
are several maples you might consider instead of ashes, including the sugar (Acer saccharum), red (A. rubrum), 'Autumn Blaze' Freeman (A. x freemanii), and Miyabe (A. miyabei). All these are hardy to at least USDA zone 4
(-20 to -30 average winter minimum temperature). The Miyabe can reach 25 feet in 10
years. 'Morton' is a miyabe cultivar
from the Morton Arboretum near Chicago, having a dense crown and dark green
leaves. 'State Street' miyabe maple is fast growing, with an upright oval
habit, yellow fall leaves, and corky outer bark.
three linden or basswood cultivars (Tilia)
in the Michigan trials have proved outstanding.
After 10 years of growth, 'Redmond' (T.
americana) is 20 feet tall, 'Greenspire' (T. cordata) is 22 feet, and American Sentry (T. americana) is 23 feet. All
are pyramidal with dark green leaves.
'Greenspire' is hardy to zone 4, the other two even colder to zone 3.
oaks (Quercus) have proven good ash
alternatives, although they may grow more slowly. The northern pin oak (Q. ellipsoidalis) may reach just over 10
feet high in 10 years, is hardy to at least zone 4, is native to the Midwest,
and doesn't get the yellowed chlorotic leaves you may find on the standard pin
oak (Q. palustris). A couple other of the more hardy oaks to
consider are the Bur (Q. macrocarpa)
and the Swamp white (Q. bicolor). Other good oaks, hardy to the warmer zone 5
found in much of central New England, include the shingle (Q. imbricaria) and the sawtooth (Q. acutissima).
ironic that some of the American elm replacements, bred to resist the Dutch elm
disease, are now recommended to replace ashes as these are taken down by the
emerald ash borer. Accolade elms are hardy to zone 4, and fast growing--
reaching 27 feet after 10 years. Triumph elm, also developed at the Morton
Arboretum as was Accolade, has a similar growth rate but is rated hardy to zone
are other good ash alternatives, including the yellow buckeye (Aesculus flava). Hardy to zone 4, this rounded tree can reach about 20
feet in 10 years. For a lower tree,
consider the American hophornbeam (Ostrya
virginiana) with its flowers resembling hops. It is hardy to zone 4, but rather slow
growing, reaching 14 feet in 10 years. Amur corktree (Phellodendron amurense) is hardy to zone 3, rounded at 40 feet
eventually, with yellow to bronze-yellow fall color, a moderate to fast growth
rate, and tolerates drought and pollution.
publication from Dr. Cregg in the MSU horticulture department (www.hrt.msu.edu)
lists many more ash alternatives. You
can get to know more about this borer, its damage, location, how to spot it, and
controls, from a joint website of the USDA Forest Service and several
universities (www.emeraldashborer.info). Make sure and
don’t move firewood around or between areas and states, as this is a main means
of distribution of such tree-damaging pests.