| Ulmus americana | |
|---|---|
'Lewis & Clark' leaves, midsummer |
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| Details | |
| Cultivar |
'Lewis & Clark' Prairie Expedition |
| Origin | North Dakota State University Research Foundation, USA |
The American Elm Ulmus americana cultivar 'Lewis & Clark' (Prairie Expedition) is a relatively new development from the North Dakota State University (NDSU) Research Foundation breeding programme, released in 2004 to commemorate the 200th anniversary of the eponymous expedition [1]. The cultivar was cloned from a tree discovered in 1994 along the Wild Rice River south west of Fargo, ND., where all those around it had succumbed to Dutch elm disease; the tree remains in perfect health (2008).
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'Lewis & Clark' is distinguished in maturity by its broad umbrella crown and dark green foliage. [2] The clone grows very rapidly, averaging an increase of > 1 m in height per annum when young, and reaching a height of up to 17 m. in 25 to 30 years [3]. The leaves are < 13 cm in length by 9 cm broad, coarsely-toothed, and with a 4 mm petiole.
Possession of an innate resistance to Dutch elm disease was suggested after inoculation with the causal fungus at the NDSU [1], however replication of the tests is considered too limited to be conclusive. No other specific information available, but the species generally is highly susceptible to Elm Yellows; it is also moderately preferred for feeding and reproduction by the adult Elm Leaf Beetle Xanthogaleruca luteola [2] [4], and highly preferred for feeding by the Japanese Beetle Popillia japonica [3] [5] [6] in the USA. U. americana is also the most susceptible of all the elms to verticillium wilt [4].
'Lewis & Clark' (Prairie Expedition) has been included in the National Elm Trial coordinated by Colorado State University. The tree is in commerce in the USA, and was introduced to the UK in 2008, but is not known to have reached continental Europe or Australasia.
The tree is named for the Lewis & Clark prairie expedition of 1804.
None known.