| Ulmus americana | |
|---|---|
| Details | |
| Cultivar | 'Iowa State' |
| Origin | Iowa State University, USA |
The American Elm Ulmus americana 'Iowa State' was discovered by Professor Alexander (Sandy) McNabb of Iowa State University as the sole surviving tree in 40 acres (16 ha) of diseased elm at Burlington [1].
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The tree is possessed of a fastigiate, thickly-branched habit, but has relatively weak crotches rendering it prone to splitting.
'Iowa State' was reported in the American Horticulturist News Edition, 63(5):4, 1984, as "a natural selection from southeastern Iowa, highly resistant to Dutch elm disease when inoculated". No other specific information available, but the species is highly susceptible to Elm Yellows; it is also moderately preferred for feeding and reproduction by the adult Elm Leaf Beetle Xanthogaleruca luteola [2] [1], and highly preferred for feeding by the Japanese Beetle Popillia japonica [3] [2] [3] in the USA. U. americana is also the most susceptible of all the elms to verticillium wilt [4].
Specimens were given to Mr. Donald C. Willeke of Minneapolis, Minnesota, former Chairman of the Minnesota and U. S. Urban Forest Councils, who planted them in that city. Most of these trees still survive; one specimen planted in 1977 attained a height of over 20 m and d.b.h. of 50 cm in 30 years. 'Iowa State' is not known to have ever been in commerce, nor is it known to have been introduced to Europe or Australasia.
None known.