A chestnut grows, flowers in St. Anthony Park

In May, if you stroll along CHELMSFORD street near Dudley in North St. Anthony Park, you’ll notice a striking, yet vaguely unfamiliar tree. That’s an American chestnut, and it certainly wouldn’t have been unfamiliar to Americans 100 years ago. Once a dominant species across the eastern United States, today American chestnut trees that survive long enough to mature and produce flowers are exceedingly rare due to a devastating disease known as chestnut blight. St. Anthony Park is not only home to one of the few mature flowering chestnut trees in Minnesota, but it was also the home of Professor Charlie Burnham, a researcher dedicated to finding resistance to chestnut blight.   

One of the best ways to recognize an American chestnut is by the unique flowers produced each spring. And what beautiful flowers they are – fragrant “catkins” that seem to resemble dozens of long white caterpillars stretching out from the ends of branches. The chestnut’s bark is dark gray and sinuous smooth with deep furrows running up and down the tree. Chestnut wood is prized as timber, substantial and rot-resistant. The nuts we all know from the holidays – though chestnuts roasting on a fire these days generally come from Europe. Back when there were four billion chestnut trees across North America, those flowers and nuts would have been essential foundations for a continental-sized ecosystem.

The demise of the American chestnut is a sad story of a disease epidemic that completely devastated the trees across North America in the first half of the 20th century. Chestnut blight is caused by the fungus, Cryphonectria parasitica. It first appeared in the U.S. in 1904 and by 1926, the disease had spread through the entire range of the American chestnut. When chestnut blight strikes a tree, it leads to certain death, though the process can take years. The fungus infects the tree through wounds in the bark. As it grows, it kills the living cells in the bark and sapwood, cutting off the flow of nutrients  and water. Eventually the infection encircles the trunk and the tree canopy dies. 

University of Minnesota Extension educator Michelle Grabowski and Plant Pathology Professor Bob Blanchette examine a chestnut flower (in spring 2018). Photo courtesy Nevin Young.

Sadly, the CHELMSFORD street chestnut is already infected with chestnut blight. Last May, when University of Minnesota Plant Pathology professor, Bob Blanchette, and Extension Educator, Michelle Grabowksi, first saw the tree, they immediately focused on cracks 15-25 feet up where the bark showed the tell-tale signs of fungal blight. Blanchette and Grabowski estimated the tree’s age at around 25 years  – but its future life expectancy is probably just a few more years due to the disease. Indeed, a second chestnut used to sit a few yards north on CHELMSFORD, but had become so diseased that it had to be cut down a few years ago.

There is the promise of resistant American chestnuts in the future. Scientists have been working for decades to develop trees that can resistant Cryphonectria. In fact a leading originator of this research was St. Anthony Park resident, Charlie Burnham, co-founder of the American Chestnut Foundation in the 1980s. At the U, Prof. Burnham’s research wasn’t tree breeding at all; he focused on corn genetics and had previously worked with Nobel prize winner, Barbara McClintock. But he had a passion for chestnuts and a vision that the right germplasm combined with strategic breeding could produce blight resistant trees. Scientists today are close to reaching that goal through the use of hybrids between Asian and American chestnuts as well as trees that express a wheat gene that makes the trees resistant.

The remarkable surviving CHELMSFORD street American chestnut, one of very few in St. Paul or all of Minnesota, will be in flower for much of May and early June.  It will probably be around for only a few more seasons. A new crop of blight resistant chestnuts may be planted someday, but they will take years to flower. Now is your best chance to see this magnificent tree in its splendor.

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