Accolade™ Elm (Ulmus 'Morton')

Accolade™ (cultivar name 'Morton') is an Asian elm hybrid developed at the Morton Arboretum in Lisle, Illinois. It combines an upright vase form similar to the American elm with the high natural DED resistance of its Asian parentage and has become one of the most widely planted resistant elm cultivars in the central United States.

Origin

Accolade™ was developed by George Ware at the Morton Arboretum from a hybrid of Japanese elm (Ulmus davidiana var. japonica) and Wilson's elm (Ulmus wilsoniana). The original seedling was selected in the 1980s after evaluation of hundreds of Asian elm hybrids for resistance, form, and urban tolerance. Commercial release followed in 1994, with subsequent licensing through Chicagoland Grows.

The cultivar trade-name "Accolade" was selected to indicate its standing among Morton's elm releases; the registered cultivar name 'Morton' anchors it taxonomically.

Identification

Form: Upright vase shape, reminiscent of American elm but more compact

Mature size: 50–60 feet tall, 40–50 foot crown spread

Leaves: Glossy dark green, oval with double-serrated margins, asymmetric base; smaller than American elm leaves (2–4 inches)

Fall color: Yellow

Bark: Gray-brown, scaly on mature trunks

Growth rate: Fast

Hardiness and adaptability

USDA hardiness zones: 4–7

Site preferences: Tolerates urban soils, compaction, salt, and a range of pH

Stress tolerance: Drought-tolerant; particularly well-adapted to Midwest conditions

Dutch Elm Disease resistance

Accolade™ demonstrates very high DED resistance, derived from its Asian parentage. In National Elm Trial evaluations (Griffin et al. 2017), the cultivar showed near-zero disease incidence over the 10-year study period across multiple locations.

The cultivar is also resistant to elm yellows phytoplasma — a feature shared by most Asian-derived elm hybrids and notably absent in pure American elm cultivars.

Landscape uses

Street trees in urban environments throughout the central United States

Park and campus plantings

Mixed cultivar palettes alongside American elm hybrids

Commercial and institutional landscapes seeking elm aesthetics with reliable disease resistance

Limitations

Hardiness limited to zone 4 minimum; less suitable for far northern climates than 'Discovery' or Prairie Expedition™

Crown is less broadly spreading than mature American elm cultivars

Performance in hot southern climates (zone 8+) is variable; better-suited cultivars exist for those regions

Asian elm aesthetics differ subtly from American elm — leaf size and bark texture distinguish the two on close inspection

Similar cultivars

Triumph™ — companion Morton release; complex hybrid background

Allee® — Chinese elm cultivar with comparable urban tolerance

Athena® — Chinese elm cultivar with smaller mature form

Related pages

What Cultivars Are Resistant to Dutch Elm Disease?

Disease-Resistant Varieties Guide

Elm Species: A Complete Guide

References

Ware, G. H. (1995). "Little-known elms from China: landscape tree possibilities." Journal of Arboriculture, 21(6), 284–288.

Griffin, J. J., Jacobi, W. R., McPherson, E. G., et al. (2017). "Ten-year performance of the United States National Elm Trial." Arboriculture & Urban Forestry, 43(3), 107–120.

Santamour, F. S., & Bentz, S. E. (1995). "Updated checklist of elm (Ulmus) cultivars for use in North America." Journal of Arboriculture, 21(3), 122–131.