Our John C. Pair Horticultural Center near Wichita established a National Elm Trial in 2007 with 18 cultivars. All of these are Dutch Elm Disease (DED) Resistant with 4 being true American elms. The cultivar ‘Jefferson’ would have been a fifth true American elm but proved to be the same cultivar as ‘Princeton’. The remainder are either hybrids or other elm species. The four true American elms are ‘Valley Forge’, ‘Princeton’, ‘New Harmony’ and ‘Lewis and Clark’ (Prairie Expedition).
All have shown excellent tolerance to DED. Characteristics listed below are primarily from our study at the John C. Pair Horticultural Center but storm breakage is from the University of Minnesota. See http://www.extension.umn.edu/environment/agroforestry/elm-trees.html for the Minnesota study.
‘Valley Forge’
Survival: 100%
Crown Shape: Vase
Lacebug damage to foliage: Minimal
European elm flea weevil damage: Minimal Storm Breakage: Fair
Comments: Strong grower, broad spreading
‘Princeton’
Survival: 100%
Crown Shape: Vase
Lacebug damage to foliage: Minimal
European elm flea weevil damage: Minimal Storm Breakage: Fair
Comments: Impressive grower, upright habit, attractive tree
‘New Harmony’
Survival: 100%
Crown Shape: Vase and round
Lacebug damage to foliage: Significant
European elm flea weevil damage: Minimal Storm Breakage: Not in Minnesota study
Comments: Narrow, upright habit with strong, central axis
‘Lewis and Clark’ (Prairie Expedition)
Survival: 80%
Crown Shape: Broad oval
Lacebug damage to foliage: Minimal
European elm flea weevil damage: Minimal Storm Breakage: Good
Comments: Strong grower with broad spreading habit, some wetwood.
Storm damage can be minimized by pruning when the tree is young.
Maintain a central leader but prune out all lower branches as the tree grows and branches increase in diameter so that there is room to work under the tree. Also prune out branches attached with a narrow angle as these are most likely to give way in ice or wind storms. For photos and more information from our John C. Pair Horticultural Center, see http://webdoc.agsci.colostate.edu/bspm/Kansas%20Elm%20Trial%20Nov%2012%202014.pdf
(Ward Upham)
