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YES, THE ELMS DIED, BUT HELP IS ON THE WAY
My brother wrote a story a while back about the "Big Elm" tree that grew at the center of our Carver County farm yard. The story was a moving account of how this majestic elm provided shade, shelter and inspiration for members of my family.
I sent the story to a friend who also grew up on a Minnesota farm and he told me later that reading it brought tears to his eyes because, he said, it triggered such powerful emotions about his youth, a big elm tree that grew on his farm, and a bygone era that cannot be resurrected.
I'm relating this story because Ulmus americana, latin for the American elm, was an important icon for much of Minnesota's first 150 years of history.
Sadly, many of the towering elms that canopied city streets and formed the hub of many a Minnesota farmyard no longer exist. Hundreds of thousands of elms died prematurely because the elm's countless desirable traits led in over-planting, which eventually led to a disease epidemic -- Dutch Elm Disease (DED).
There is a long list of reasons that so many elms flourished for so long in Minnesota. Minnesota tree expert Mark Stennis, an certified arborist with Top-Notch Tree Care, says American elm's most endearing feature is its unique vase-shape habit of growth that dominates a space when planted in the open, and forms an arch-like cathedral when planted in rows.
Elms were planted everywhere for so many years, Stennis says, because they thrived amid the urban stresses of narrow, compacted boulevards and next to curbs and sidewalks. They could tolerate low-oxygen levels in soil associated with compaction and impervious surfaces and withstood flooding, salt, a wide pH range, and annual rainfall swings from 15-60 inches. They even survived the stresses of home construction in the post-WWII housing boom, often growing trunk girths of 6 feet or more just yards from the back doors of countless Minneapolis and first-ring suburb houses.
Sadly, the strength and beauty of the elm is just a memory now except for a small percentage of the original elm population that lives on thanks to rare natural tolerance for the disease or expensive chemical injections.
The good news about the American elm is that plant breeders have made great strides in discovering disease-tolerant elm varieties that can now be purchased and planted in our yards. The new varieties won't deliver all the positive traits that were found in American elm prior to DED but there is a growing list of elms that show promise of being able to live in the presence of DED.
One reason researchers have had trouble breeding disease-resistant American elms has to do with the complex biology of American elm genes (American elms have "tetraploid genes" - too complicated for me to understand!). As a result, researchers have had to select by propagating tissue samples from American elm specimens that have survived in the presence of severe DED infestations.
Two DED-tolerant clones of American elm are "Valley Forge" and "New Harmony." The growth rate of these two varieties is phenomenal, according to Stennis. Referring to a young Valley Forge elm tree he started from a root cutting in 2000, Stennis said its growth "took off like a scalded dog."
Another elm variety that tolerates the DED fungus is named "Princeton" and can be obtained from a New Jersey nursery (www.riveredgefarms.com).
There is a 72-inch diameter American elm with a 100 ft. crown spread growing near Afton, Minnesota that has survived DED even as elms all around it have perished. Root cuttings from this tree have been propagated in trials and may be available in nurseries this year or in the near future.
Stennis says that it is important that we (as consumers) show some interest in these DED-resistant or tolerant varieties because local nurseries will not grow them if nobody steps up to buy them.
"If you want an elm, ask for it," Stennis says. If a nursery claims they cannot provide one of the new elm varieties, he recommends returning to your car and continuing your search. Seeing a sale walk out the door is powerful incentive to nurseries to get on-board the elm re-population campaign, according to Stennis.
"There are thousands of good growing sites for disease-tolerant American elm trees," Stennis concludes. "We are in no danger of having too many elms."
More information about ongoing elm research and evaluations at the University of Minnesota can be viewed at the website www.tre.umn.edu.
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