What Is The American Liberty Elm?
The American Liberty Elm has a record of more than 27 years of street-testing. It is the only street-proven resistant elm with a Lifetime Warranty against Dutch elm disease (DED.)
When we began our mission to save the American elm, our goal was to find a native American elm which was at least resistant but not necessarily immune to DED. Our research to develop a genetically resistant cultivar dates back to trees which we inherited from the Cornell University arboretum, survivors from over 20,000 trees Cornell began to screen in 1933. We continued the screening process, beginning in the 1970's, at the University of Wisconsin using their elm plot of 17,000 trees. The Liberty Elm parents that survived the initial screening then went through extensive lab tests including eight inoculations of 10 Dutch elm disease fungus isolates collected from the northern range of North America.
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When researchers first developed their method for inoculating the trees, with the fungus, they cautioned us that this was merely an imitation of nature, not to be considered comparable to a field-test where the beetle in feeding on new wood introduces the fungus into the vascular system of the tree at many different locations. They stressed that resistance did not infer immunity. Losses should be expected, perhaps up to 10%. After these extensive tests, it appeared they were resistant and were ready to move on to the next test--field tests (also called street testing.)
Our goal was to have a 90% survival rate demonstrated through field tests. Now after more than 27 years of field tests where it has been exposed naturally to DED fungus where it may occur in those environments. Our losses are still under 1% based on the cases of DED reported to us by our growers. Since 1983, volunteers around the country have been nurturing the pure-American Liberty Elm. They've planted over 300,000 of them in thousands of communities in 45 states.
The Liberty Elm is not a hybrid. ERI's American Liberty Elm is actually a group of six genetically different cultivars. All six look like classic, old fashioned American elms. You have to look closely and know what you're looking for to tell the difference among the six. To be sure which one you have you really need to have DNA analysis.
Genetic differences provide diversity. Having six cultivars in the series is insurance against all the elms being wiped out by any disease or problem, even one that might show up in the future.
There is no known American elm variety that can be called entirely immune to DED. Each Liberty Elm carries a Lifetime Warranty against DED. ERI agrees to replace this tree if it succumbs to Dutch elm disease.