Of course I'm just guessin', but likely that "spiral grain" elm is just another variant of the Siberian Elm.
At one time, before it proved to be invasive, the Siberian Elm was thought to possibly be the "replacement" for the American Elm that was being devastated by DED. Dozens of cultivators were developed and tested... it was crossed with all sorts of elms, both domestic and imported. Many of those cultivators "went wild", and "in the wild" the Siberian Elm naturally breeds the engineered genes out... eventually becoming plain ol' Siberian Elm again. The thing is, many of those original cultivators are still living, planted in shelter belts, farmyards, and even along city streets of the Midwest and plains... and they're still makin' seeds and escaping into "the wild".
The worst thing about the Siberian Elm (we now know) is that it naturally hybridizes "in the wild" with the Slippery (Red) Elm, and eventually breeds the Slippery elm out of existence. There are areas of the Midwest and plains where the Slippery Elm is all but extinct because of the double hit... the double hit of DED and Siberian Elm. That's one of the reasons the Siberian Elm was thought to be a replacement for the American Elm... both the Slippery and Siberian Elms showed a certain amount of resistance to DED, and the two were easily hybridized. Where we went wrong was, it wasn't so much that the trees were resistant... it was more that DED had a preference for American Elm. Once the American Elm was all but gone, DED simply morphed itself into something with a preference for Slippery Elms, Siberian Elms, and the hybrids. The lone holdout is the Rock Elm... but its time is coming.
I have several very large American Elms, and a few big Slippery Elms in my woodlot that have survived several onslaughts of DED. But each time DED makes another pass it gets more of them... the disease morphs as needed to stay alive. Smaller trees spring up from the larger "resistant" trees, only to be wiped out during the next pass from DED. My woodlot will go three, four, maybe five years without a sign... and then suddenly dozens will die in just a couple years. The cycle repeats itself over and over. Some of the young trees will survive a couple passes, but I have virtually no elms between the 8-10 inch diameter and the 24-30+ inch diameter... they just don't make it long enough to get bigger than 10 inches, and the last of the bigger ones will soon be gone.
The whole mess is a sad state of affairs...
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