Ulmus americana 'Iowa State'

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Ulmus americana
Cultivar 'Iowa State'
Origin Iowa State University, USA

The American Elm cultivar Ulmus americana 'Iowa State' was cloned from a tree discovered by Professor Alexander (Sandy) McNabb of Iowa State University as the sole survivor in 40 acres (16 ha) of diseased elm at Burlington.[1]


The tree is possessed of a fastigiate, thickly-branched habit, but has relatively weak branch unions owing to acute angles of attachment leading to bark inclusions. One of the original plantings (1978) in the Dean Park area of Minneapolis had to be felled in 2012, 34 years later, after serious defects developed.[2]

Pests and diseases[edit]

'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 [3] [2], and highly preferred for feeding by the Japanese Beetle Popillia japonica [4] [3] [4] in the United States. U. americana is also the most susceptible of all the elms to verticillium wilt.[5]


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.


  • 'Iowa State University': Anon.


None known.


  1. ^ Santamour, Frank S.; Bentz, Susan E. (May 1995). "Updated Checklist of Elm (Ulmus) Cultivars for use in North America". Journal of Arboriculture. 21 (3): 122–131. Retrieved 20 June 2016. 
  2. ^ Blair, (2013). Goodbye to 'Iowa State'. Elm Archives - Trees. University of Minnesota. [1]
  3. ^ Miller, F. and Ware, G. (2001). Resistance of Temperate Chinese Elms (Ulmuss spp.) to Feeding of the Adult Elm Leaf Beetle (Coleoptera: Chrysomelidae). Journal of Economic Entomology 94 (1): 162-166. 2001. Entom. Soc.of America.
  4. ^ Miller, F., Ware, G. and Jackson, J. (2001). Preference of Temperate Chinese Elms (Ulmuss spp.) for the Feeding of the Japanese Beetle (Coleoptera: Scarabaeidae). Journal of Economic Entomology 94 (2). pp 445-448. 2001. Entom. Soc.of America.
  5. ^ Pegg, G. F. & Brady, B. L. (2002). Verticillium Wilts. CABI Publishing. ISBN 0-85199-529-2