| Ulmus hybrid | |
|---|---|
| Details | |
| Hybrid parentage | U. pumila × U. davidiana var. japonica |
| Cultivar | 'Morton Plainsman' = Vanguard™ |
| Origin | USA |
The elm cultivar 'Morton Plainsman' (Vanguard) is another Morton Arboretum selection derived from a crossing of the Siberian Elm U. pumila and the Japanese Elm U. davidiana var. japonica grown from openly-pollinated seed donated by the Agriculture Canada Research Station at Morden in Manitoba.
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The tree has modest upright growth, increasing in height by an average of 0.8 m in an assessment at U C Davis,[1] with leaves much the same size and colour of the American Elm. [1] However, its performance in the southern United States has not impressed, and it was dismissed, along with its Morton stablemates 'Morton Stalwart' (Commendation) and 'Morton Glossy' (Triumph), as "ugly" by Michael Dirr, Professor of Horticulture at the University of Georgia [2], on account of its "wild" growth and splaying branches.
Although resistant to Dutch elm disease, 'Morton Plainsman' (Vanguard) remains very susceptible to pests such as the elm-leaf beetle Xanthogaleruca luteola [1] [3], Japanese beetle,[2] and cankerworms.
In trials at the University of Minnesota, 'Morton Plainsman' was found to have the second highest, after 'Morton Red Tip' (Danada Charm ), incidence of branch breakage occasioned by bark inclusions.[3] However, the tree has a high degree of drought and cold tolerance making it particularly suitable for afforestation in the Great Plains.[4][5] In artificial freezing tests at the Morton Arboretum [6] the LT50 (temp. at which 50% of tissues die) was found to be - 40 °C.
The tree is currently being evaluated in the National Elm Trial [4] coordinated by Colorado State University. It is not known to have been introduced to Europe or Australasia.
'Morton Plainsman' (Vanguard) was crossed with the hybrid cultivar 'Morton' (Accolade). A selection of the resultant seedlings was marketed under the name 'Charisma', later changed to 'Morton Glossy' (Triumph).