Generations ago, stately American elms lined the streets in many of our cities and towns, their arching branches creating a canopy of leafy shade. Then imported Dutch elm disease (DED) struck. First identified in Ohio in 1930, it moved across the country, killing off most of the elms in urban areas, leaving streets bare of greenery. Many of these streets have been replanted with a variety of trees, as the loss of the elms taught a lesson in the danger of planting a monoculture of just one kind of tree. But few other trees display the elegant, vase-shaped growth habit of the American elm, and researchers have been on a quest to find an American elm cultivar or another, similarly-shaped species or hybrid to take its place in our landscapes and along our streets.
One such tree is the Accolade™ elm (Ulmus 'Morton'), which was named the 2012 Urban Tree of the Year by the Society of Municipal Arborists. This elm is a hybrid, a cross between two Asian species, Ulmus japonica and Ulmus wilsoniana. Its mature habit is upright and arching, similar to that of the American elm, but more compact, with an expected height of 40-60 feet and spread of 35-40 feet at maturity. Reliably hardy to Zone 4, it is resistant to DED (but not immune), as well as elm yellows, and does not appear to be overly susceptible elm leaf beetle infestations. A vigorous, fast grower, it transplants easily, tolerates a wide range of soil conditions, including alkaline soil, and displays nice yellow fall color.
The original elm from which Accolade™ is propagated (pictured) was planted at the Morton Arboretum in Ohio in 1924 from seed distributed by Boston's Arnold Arboretum, where it grows to this day, having survived three epidemics of DED at the arboretum over its more than 80 year life span so far.
For more information about the Accolade™ elm, go to: Tree of the Year.