| Ulmus hybrid | |
|---|---|
Commendation Elm [1] |
|
| Details | |
| Hybrid parentage | 'Morton' (Accolade) × (U. pumila × U. minor). |
| Cultivar | 'Morton Stalwart' = Commendation™ |
| Origin | USA |
The Elm tree Ulmus 'Morton Stalwart' (Commendation), is a Morton Arboretum hybrid from a controlled crossing of 'Morton' (Accolade) with a Ulmus pumila × U. minor (syn. carpinifolia) [2] from eastern Russia.[3]
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The branches are upright, but the form of the tree is more oval than vase-shaped; the leaves are relatively large. However, examples grown in the warmer climes of the southern United States have not impressed, and it was dismissed, along with its Morton stablemates 'Morton Glossy' (Triumph) and 'Morton Plainsman' (Vanguard), as 'ugly' by Michael Dirr, Professor of Horticulture at the University of Georgia [1], on account of its 'wild' growth and splaying branches.
Although resistant to Dutch elm disease, the tree is moderately susceptible to insects,[3] notably elm leaf beetle Xanthogaleruca luteola,[4] Japanese beetle [5] and Gypsy moth.
'Morton Stalwart' is vigorous and robust, adjudged the third fastest-growing cultivar of 17 assessed by the University of Minnesota and fourth out of 15 in trials at U C Davis;[4] it is also extremely tolerant of drought [6] and cold. In artificial freezing tests at the Morton Arboretum [7] the tree was found cold-hardy to -40 °C.
'Morton Stalwart' was introduced by Chicagoland Grows Inc.,[3] and is currently being evaluated in the National Elm Trial[8] coordinated by Colorado State University. The tree is not known to have been introduced to Europe or Australasia.