When it comes to street trees, many of us “older and wiser” folks remember driving down a residential street surrounded by a canopy of American elm trees. However, back in the late 60’s and early 70’s, arborists started removing thousands of dead elms, including my Detroit, Michigan street tree. This moment was a pivotal point in my “budding” career as a young child; I wanted to know why the trees were removed and what I could do to help.
Once widely planted and used for its form, shade and incredible urban tolerance, the American elm succumbed to Dutch elm disease (DED), spreading rapidly by elm bark beetles and root grafts between elm trees. Did this mean no more elm trees in our urban forest? Scientists at major universities and arboreta across the U.S. worked on solutions. From their breeding efforts, new hybrids of various species of American, Asian and European elms were created. Many of these trees show good resistance to DED and phloem necrosis (elm yellows), another devastating disease of elms. Through many years of breeding, evaluation and selection, we are now able to bring more elms back to our urban forests.
The below species, hybrids and cultivars are all commercially available in Wisconsin or available from one of the large, bareroot tree nurseries that supply elms to Wisconsin nurseries. I have researched their availability for you and omitted elms that are no longer available for sale, including several American elm cultivars. As newer selections become available with better form or growth rate and improved insect and disease resistance, older hybrids are no longer available. Resistance to leaf feeding insects should be part of your selection process. Elm leaf beetle, Japanese beetle, elm leaf miner, cankerworms, etc. can severely alter the ornamental value of a tree, i.e. defoliation or severe leaf browning in summer, similar to littleleaf linden trees.
I. Ulmus americana (American elm); hardy to zone 3-4 (depends on cultivar); height and width vary with cultivar, but the American elm hybrids all have the classic, vase-shaped form; native to eastern and central U.S. and Canada; available cultivars are listed below
U.S. National Arboretum Introductions
‘Jefferson’: hardy to zone 4; 70’ tall, 50’ wide; upright, vase-shaped form, deep green leaves, DED resistant
‘New Harmony’: hardy to zone 4b-5a; 70’ tall and wide; broad, vase-shaped crown with arching branches; DED resistant
‘Valley Forge’: hardy to zone 4; 60-80’ tall, 60-70’ wide; upright, vase-shaped form with arching branches, but with wild-looking branches that need training pruning when young to develop good form; DED resistant; resistant to elm leaf beetles, but very susceptible to Japanese beetles
Other Nursery Introductions
‘JFS-Prince II’: Colonial Spirit®, hardy to zone 4; 65’ tall, 50’ wide; vase-shaped form with arching limbs; good branch structure and more symmetrical; DED resistant; J. Frank Schmidt and Son Nursery Introduction
‘Lewis and Clark’: Prairie Expedition®, hardy to zone 3a; 55’ tall, 60’ wide; rounded to spreading, vase-shaped form; fast grower; dark green leaves; selection from Fargo, ND; DED resistant; Bailey Nurseries introduction
‘Princeton’: hardy to zone 4; 60-80’ tall, 40-60’ wide; more upright to vase-shaped form; does require shaping pruning when young to develop good branch structure; large, leathery leaves; moderately resistant to elm leaf beetles, but very susceptible to Japanese beetles; DED resistant; Princeton Nursery introduction
‘St. Croix’: First Editions® St. Croix™, hardy to zone 3; 60-75’ tall, 70-90’ wide; broadly vase-shaped to spreading form; dark green leaves; DED resistant; from a Minnesota selection; Bailey Nurseries introduction
II. Other non-American elm species, hybrids and cultivars
Ulmus davidiana ‘JFS-KW2UD’: Greenstone™ David elm, hardy to zone 4; 60’ tall, 40’ wide; upright,
vase-shaped form; vigorous grower; strong branching with wide branch crotch angles; DED and phloem necrosis resistant; resistant to elm leaf beetle and elm leaf miner
Ulmus davidiana var. japonica: Japanese elm; (formerly listed as Ulmus japonica, Ulmus propinqua and Ulmus wilsoniana;all combined now under U. davidiana var. japonica); cultivars listed below; native to Japan and Asia
’Discovery’: hardy to zone 4; 35-40’ tall and wide; more upright to vase-shaped, compact form; prone to co-dominant leaders; dark green leaves; DED resistant and resistant to elm leaf beetle; good drought tolerance; selection from Manitoba, Canada
‘JFS-Bieberich’: Emerald Sunshine® (formerly listed as U. propinqua): hardy to zone 5; 35’ tall, 25’ wide; vase-shaped form; dark green, glossy, corrugated leaves; DED and phloem necrosis resistant; resistant to elm leaf beetle and Japanese beetles; selected on western Oklahoma plains; J. Frank Schmidt and Son Nursery Introduction
‘Prospector’ (formerly listed as Ulmus wilsoniana): hardy to zone 5a; 40’ tall, 30’ wide; dense, broad, vase-shaped form with slightly pendulous branches; vigorous grower that will require shaping pruning to develop good branch structure; deep green, glossy leaves; DED and phloem necrosis resistant; resistant to elm leaf beetles, but is susceptible to leaf hoppers and Japanese beetles; U.S. National Arboretum introduction
UW-Madison Hybrid Elm Introductions
‘Cathedral’: (hybrid of U. pumila ´ U. japonica); hardy to zone 4b-5a; 40-50’ tall, 40-60’ wide; broad, vase-shaped form that becomes more spreading with age; vigorous grower and will require shaping pruning to maintain form; prone to included bark formation; larger green leaves; DED resistant; susceptible to elm leaf beetles and leaf hoppers
‘New Horizon’: (hybrid of U. japonica ´ U. pumila); hardy to zone 4; 50-60’ tall, 40-50’ wide; upright to vase-shaped form; vigorous grower; wide branch crotch angles; slightly arching branches; can produce co-dominant leaders; requires shaping pruning to develop good branch structure; larger, dark green leaves; DED resistant, but some susceptibility to Verticillium wilt; resistant to elm leaf miner, but very susceptible to elm leaf beetles
‘Regal’: (complex hybrid of U. carpinifolia ´ (U. pumila ´ U. ´ hollandica), hardy to zone 4; 50-60’ tall, 30-35’ wide; narrow, upright form when young becoming oval to pyramidal with age with a straight terminal leader and wider branch crotch angles; it is not vase-shaped; can produce co-dominant leaders; large, dark green leaves; DED resistant, but there was a report in Madison of a ‘Regal’ elm that died from DED; some susceptibility to elm leaf beetle and cankerworms
U.S. National Arboretum Hybrid Elm Introductions (Washington, D.C.)
‘Frontier’: (hybrid of U. carpinifolia ´ U. parvifolia); hardy to zone 5; 40-50’ tall, 30’ wide; broadly oval to vase-shaped form with ascending branches; glossy, dark green, small leaves; showy, deep burgundy fall color late in the season; gray bark with orange lenticels; DED resistant; moderate resistance to elm leaf beetles; do not bareroot transplant this one due to U. parvifolia as one parent
‘Homestead’: (complex hybrid of U. pumila ´ U. ´ hollandica ´ U. carpinifolia); hardy to zone 4b; 55’ tall, 35’ wide; narrow, oval form with upright, arching branches; not vase-shaped; vigorous grower; dark green leaves; DED resistant, but there are a few reports of DED on ‘Homestead’; very susceptible to elm leaf beetles and elm flea weevils and other leaf feeding insects
‘Patriot’: (complex hybrid of U. wilsoniana, U. pumila, U. carpinifolia, and U. glabra); hardy to zone 4b; 50’ tall, 40’ wide; stiffly upright, to narrow, vase-shaped form with age; dark green, glossy leaves; DED resistant; elm leaf beetle resistant
‘Pioneer’: (hybrid of U. glabra ´ U. carpinifolia); hardy to zone 5; 50’ tall and wide; rounded form; vigorous grower and will require shaping pruning to develop good form; dark green leaves; DED resistant; highly susceptible to elm leaf beetles and other leaf feeding insects
Morton Arboretum Hybrid Elm Introductions (Lisle, IL)
‘Morton’: Accolade®, (hybrid of U. japonica ´ U. wilsoniana, both now listed as U. davidiana var. japonica); hardy to zone 4b-5a; 50-60’ tall, 30-40’ wide; vase-shaped form with upright, arching branches; vigorous grower and will require shaping pruning to develop good form; glossy, dark green leaves; DED and phloem necrosis resistant; but there were reports in Minnesota of two Accolade® elms that died from DED, however, an overall excellent rating for DED; moderately resistant to elm leaf beetles, Japanese beetles; good drought tolerance; available through the Chicagoland Grows Plant Introduction Program
‘Morton Glossy’: Triumph™, (complex hybrid of Vanguard™ ´ Accolade®); hardy to zone 4; 50-60’ tall, 40-50’ wide; oval form with upright, arching branches; vigorous grower, but easy to train in nursery; very glossy, dark green leaves; DED and phloem necrosis resistant; elm leaf beetle, Japanese beetle and cankerworm resistant; good drought tolerance; available through the Chicagoland Grows Plant Introduction Program; one of the best elms in my opinion
‘Morton Plainsman’: Vanguard™, (hybrid of U. japonica ´ U. pumila); hardy to zone 4; 45-50’ tall, 40-50’ wide; rounded form becoming more vase-shaped with age; vigorous grower and will require shaping pruning to develop good form; dark green leaves; DED and phloem necrosis resistant; susceptible to elm leaf beetles, elm leaf miner, cankerworms and Japanese beetles; good drought tolerance; available through the Chicagoland Grows Plant Introduction Program
‘Morton Red Tip’: Danada Charm™, (complex hybrid of (U. japonica ´ U. wilsoniana) ´ U. pumila); hardy to zone 4; 60-70’ tall; 50-60’ wide; rounded when young becoming vase-shaped with age; vigorous grower that requires shaping pruning to develop good form; red-tinged, new leaves turn dark green in summer; DED and phloem necrosis resistant; susceptible to elm leaf and Japanese beetles, cankerworms, and gypsy moth; available through the Chicagoland Grows Plant Introduction Program
‘Morton Stalwart’: Commendation™, (complex hybrid of Accolade™ ´ (U. pumila ´ U. carpinifolia); hardy to zone 4b-5a; 50-60’ tall, 40-50’ wide; upright, oval form; symmetrical, arching branches; vigorous grower; large, dark green leaves; DED resistant; susceptible to elm leaf and Japanese beetles and gypsy moth; good drought tolerance; available through the Chicagoland Grows Plant Introduction Program
Elm species used in breeding DED resistant elms:
Ulmus americana: American elm
Ulmus carpinifolia: smoothleaf elm (now called U. minor)
Ulmus glabra: Scotch elm
Ulmus ´ hollandica: Dutch elm (hybrid of U. carpinifolia ´ U. glabra)
Ulmus japonica: Japanese elm, (now lumped under U. davidiana var. japonica)
Ulmus propinqua: (now lumped under U. davidiana var. japonica)
Ulmus wilsoniana: (now lumped under U. davidiana var. japonica)
Ulmus minor: smoothleaf elm (formerly U. carpinifolia)
Ulmus parvifolia: lacebark elm
Ulmus pumila: Siberian elm
– Dr. Laura G. Jull, Dept. of Horticulture, UW–Madison