University of Vermont Extension 
Department of Plant and Soil Science

Anytime News Article
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ASH TREE ALTERNATIVES
 
Dr. Leonard Perry, Extension Professor
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.
           
These ornamental 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.
           
Even 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.
           
There 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.
           
All 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.
           
Several 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). 
           
It's 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 5.
           
There 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. 
           
A 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.
   

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