Arboretum News

Good-bye to a Good Tree

The bur oak outside the Wilson Rose Garden suffered from Bur Oak Blight.

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The bur oak outside of the Wilson Rose Garden on Feb. 10. Photo by Liz Potasek.

By Liz Potasek

The majestic bur oak that stands outside the entrance to the Wilson Rose Garden has been a fixture on the land since before there was a Minnesota Landscape Arboretum. But for the past few years, it has clearly been struggling. The tree has Bur Oak Blight, leading to leaf loss and branch dieback, and last May Arboretum staff decided to remove the tree.

In the next few weeks, the crown of the tree will be removed, leaving a large portion of the trunk. Plans are being made to turn the trunk into an art piece, and another tree will be planted nearby. “This is a tree that means a lot to a lot of people, so we want to honor it,” says Erin Buchholz, the Arboretum’s integrated pest management specialist.

SHARE YOUR STORY
Do you have memories or photos taken with the bur oak? Please share them with us by emailing arbpr@umn.edu.

Bur Oak Blight, caused by the fungus Tubakia iowensis, was first identified in 2005, but Minnesota Department of Natural Resources Forest Health staff started noticing symptoms in the 1990s before scientists identified the cause, according to the Minnesota DNR. It’s a native fungal pathogen that’s aided by excessively wet springs and climate change. “Since bur oak blight is a relatively new phenomenon, we don’t yet know its long-term impact on Minnesota,” writes the DNR.

Symptoms of Bur Oak Blight usually appear on trees in mid-July when leaves begin showing discoloration of veins. The fungal leaf disease spreads on infected leaves, containing spores on petoiles, that remain on the tree over the winter. Bur Oak Blight can lead to other more severe problems, like Armillaria root rot and two-lined chestnut borer, aiding in the tree’s decline.

The bur oak on May 16. Photo by Erin Buchholz.

The first mention of a potential problem at the Arboretum came in 2012 when our then integrated pest management specialist made a note: “Wilson Rose Garden. Bur Oak Blight – monitor.” 

In consultation with S&S Tree and Horticultural Specialists, Arboretum staff decided to try treating the tree. The tree was injected with propiconazole, a fungicide that can help healthy trees overcome Bur Oak Blight, in 2013, 2015 and 2017. The propiconazole injections fried the leaves (a side effect that an otherwise healthy tree could likely overcome).

When Buchholz started in 2018, the tree wasn’t due for an injection. Given that the fungicide injections seemed to be causing a lot of stress to the tree, Buchholz and others decided in 2019 to reduce the stress on the tree by using Cambistat, a tree growth regulator.

This spring as other oak trees at the Arb started leafing out, the bur oak was missing its leaves. It became clear that there wasn’t much left to do for the tree. “I was absolutely heartbroken at that point,” Buchholz says. “I emailed my bosses, and we decided that treatment efforts had failed.”

Buchholz invited a University of Minnesota tree researcher to the Arboretum to look at the tree. The expert determined the tree was possibly about 180 years old. “It’s a good life span,” Buchholz says. “It’s nothing to shrug at.”

In the next few weeks, the lateral limbs of the tree will be removed. Eventually, the trunk, which doesn’t appear to have any decay, will be turned into a piece of art.

LEARN MORE
Want to know more about bur oak?  Listen to Integrated Pest Management Specialist Erin Buchholz discuss the tree as a part of a recent Bur Oak Webinar

UPDATE: The limbs of the tree were removed on Aug. 26.

Bur Oak on August 26, after crews finished trimming back the branches. Photo by Erin Buchholz.

7 comments on “Good-bye to a Good Tree

  1. DIANE E OLSON

    I’ve loved this tree forever! I’m glad you are saving the trunk for a work of art to memorialize this beauty. I remember well when the colorful streamers of cloth were hanging from the tree a number of years ago. It wore them well. Thank you great Bur Oak!

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  3. Bart Ellson

    That is a beautiful tree and it is sad to see it go. It had a pretty good life if it is indeed 180 years old or so. One possible piece of art made out of the trunk could be a thick slice of the trunk where the annual rings would be exposed. On that a timeline could be made of important events in this nation’s, states, or maybe the Arboretum’s history. Some of the other parts of the tree will be used by the Arboretum Auxiliary Woodworkers for making beautiful, unique, and useful wood products for sale at various Auxiliary sales. People who buy these products not only get a piece of that old majestic Bur Oak, but help support the Arboretum as 100% of the sales goes back to the Arboretum.

    Bart Ellson (Arboretum Auxiliary Woodworking Chair)

    • Hi, Bart! We are looking into asking a dendrochronologist to help us create a display dating the tree rings from a “cookie” of the trunk. I think the intent for the rest of the trunk is to create a work of art that would stay at the Arboretum for all to enjoy.

  4. Thank you so much for the detailed background on this particular bur oak, its demise, and upcoming removal. As a frequent visitor and Nature Notes blogger, I too had grown increasingly worried about the tree during these past several years. It clearly was no longer the same tree that I had known and grown to love over my visits in the 1990s and 2000s. I was especially fond of the way the branches extended below the base of the trunk — due to the tree position on the hillside. Wishing safety to the forestry crew in the gargantuan task ahead of them. – Greg

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