North American Hybrid Elm Trees
Being difficult to propagate, American Elm hybrids have been slow to become available. Other species displaying the classic vase shape of the American Elm have been cultivated in recent years.
Ulmus Japonica x Wilsoniana ‘Morton’ Accolade Hybrid Elm
Zones: 4-7, perhaps to zone 3
Sun
Height: 60-90’
Spread: 40-50’
Shape: Broad to upright vase shaped crown
Growth Rate: Medium to fast
Soil Preference: Tolerant of loam or sand, moderate tolerance to clay
Moisture: Average moisture needs, high drought tolerance, moderate tolerance to wet conditions
Foliage: Glossy dark green, relatively small
Blooms: Inconspicuous small green flowers in early spring
Fruit: Small, flat, round samara
Developed at the Morton Arboretum, this hybrid clone has shown good Dutch Elm disease resistance, elm leaf beetle and elm leaf miner resistance. It is the most similar in appearance and form to the American Elm, displaying the elegant vase shape crown. The leaves are a dark glossy green through the growing season, turning a pleasant golden yellow in fall. Like the tree’s parent, japonica, ‘Accolade’ grows quickly when young, more moderately as it matures. Like the most elms, the root system is shallow but extensive. ‘Accolade’ is vigorous and also possesses the tough urban tolerance of the American Elm, with the exception of only moderate tolerance to clay and compacted soil. ‘Accolade’ should become more widely available quickly due to it’s excellent characteristics. It is also known as the Thornhill Elm.
Ulmus carpinifolia x Ulmus parvifolia ‘Frontier’
Zones: 5-8 or 9
Sun to part sun
Height: 30-50’
Spread: 25-35’
Shape: Upright with a broadly oval, symmetrical crown
Growth Rate: Fast, 12-18” per year
Soil Preference: Adaptable and tolerates poor soil, prefers acid to neutral
Moisture: Prefers moist well drained, high drought tolerant
Foliage: Small dark green leaves in summer, burgundy red in fall
Blooms: Rarely flowers
Fruit: Seedless
‘Frontier’ is a smaller elm shade tree introduced by the National Arboretum. Unusual foliage emerges reddish in spring, turning green in summer, then turns a lovely purple red in fall. The small stature lends itself well to smaller properties, under power lines and as a street tree. It grows quickly, reaching about 25 feet tall with a crown spread of 15 feet within 20 years. ‘Frontier’ grows with a somewhat strong central leader and upright growth. This hybrid exhibits a high resistance to Dutch Elm disease and a moderate resistance to the elm leaf beetle. This is one of the few elms that shows high resistance to the natural infection of elm yellows. It transplants easily and grows well in a wide range of climates form the east to west coast and Ohio to Oklahoma, being very tolerant of urban conditions. ’Frontier’ is an excellent urban tree.
Ulmus pumila x Ulmas japonica ‘Sapporo Autumn Gold’
Zones: 2-5
Sun to part sun
Height: 60’
Spread: 40’
Shape: Upright, oval to somewhat vase shaped
Growth Rate: Fast, 12-18” per year
Soil Preference: Prefers loam but adapts well to clay, pH 5.8 - 8.0
Moisture: Prefers moist well drained, drought tolerant
Foliage: Small and narrow glossy green leaves, emerging with a red tinge.
Blooms: Dark red purple flower in spring
Fruit: Small round samara in spring
‘Sapporo Autumn Gold’ is a large shade elm cultivated at the University of Wisconsin. Its’ growth habit is upright with a somewhat vase shaped crown. Young trees exhibit a conical form, potentially developing a somewhat vase shaped crown as it matures. The crown is dense with irregular branching. Leaves turn a bright gold in fall, a richer color than the English Elm. The wood tends to be stronger than the Asian elms. When young, this tree produces vigorous side shoots that need to be kept pruned off. ‘Sapporo Autumn Gold’ resists leaf scorch, but does not perform well in hot arid conditions. Resistance to Dutch Elm disease is very high. Will tolerate exposed sites, making it a good selection for windbreaks.
Hybrids that are Dutch Elm disease resistant continue to be developed and researched, with many new varieties available in recent years. Complete data is still difficult to find, but your local nursery should have information about the varieties available in your area. Here is some basic information about other new hybrids developed for North America:
Ulmus pumila x Ulmus japonica ‘Cathedral’
Another University of Wisconsin introduction that is not quite as resistant to Dutch Elm disease as the ‘Sapporo Autumn Gold’. However it is highly tolerant of Verticillium wilt and elm leaf minor. Growth habit is broad with a classic vase shape. Foliage is medium to light green. Hardy to zone 4
Ulmus pumila x other hybrids ‘Homestead’
‘Homestead’ is a complex hybrid with multiple parents. It reaches 55’ high with a spread of 35’ wide and is hardy to zone 5. It is fast growing, 12’18” per year, with an upright growth habit and narrow oval or pyramid shaped crown and arching branches. The form is pleasant for a street tree. Leaves are dark green, turning yellow in fall.
Ulmus japonica x Ulmus pumila ‘New Horizon’
‘New Horizon’, yet another University of Wisconsin introduction, is resistant to Dutch Elm disease, elm leaf miner, and has a high tolerance to Verticillium wilt. It reaches 40’ high with a spread of 25’ with an upright growing habit. The crown develops to a compach oval with slightly arching branches. Large leaves are dark green with rusty red tints in the fall. It has a finer textured appearance than most elms. Hardy to zone 4.
Ulmus ‘Urban’ x Ulmus wilsoniana ‘Patriot’
‘Patriot’ is a complex hybrid crossed between the hybrid ‘Urban’ and wilsoniana that was introduced by the US Department of Agriculture. It is resistant to Dutch Elm disease and is highly tolerant to the elm leaf beetle. Growth habit is upright and stiffly vase shaped. It reaches 50’ high and spreads to 40’ wide. Although it is roughly vase shaped, the crown may remain narrower than most elms. ‘Patriot’ is hardy to zone 5.