May 2023

Hi all, 

It’s been a great quarter. There has been a lot of energy going into eastern hemlocks these few months, including the creation of lingering hemlock monitoring protocols we could use some professional feedback on (see our "Partner Spotlight" below). We are looking forward to the coming growing season, a great time for assessing lingering ash and beech!

 — Rachel Kappler

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The Latest

American beech updates:

  • Although we have to contend with beech leaf disease, we are still interested in reports of trees that are potentially resistant to beech bark disease (see Get Involved below). These trees can be locally conserved via grafting. Beech tree conservation is especially important as it is very difficult to keep beech seeds preserved.

Ash updates: 

  • Lingering ash searches are taking on more systematic methods and partners in PA (Allegheny National Forest), OH, and MI are making it one of their top priorities this season.
  • A lingering green ash orchard has been successfully planted in Brighton, MI.
  • The USFS N Research Station Ohio campus grafted new lingering ash accessions to be assessed for EAB resistance in the future. They were able to complete 13 from Ohio, 17 from Pennsylvania, 5 from Wisconsin and 1 from New Hampshire. Way to go, that's a lot of tree grafting when each accession needs at least 12 copies.

Grafted green ash at the Delaware, OH Forest Service greenhouse. Photo: R. Kappler

Eastern hemlock updates: 

  • The Lingering Hemlock Workshop on April 18th was a great endeavor that allowed for all of those interested in future resistance breeding to learn more about what has been done previously and what is up and coming.
  • Thanks to all of those who also participated in the discussion period on the lingering hemlock monitoring protocols. The working group is accepting feedback on the hemlock protocols through May 31! Visit our website to view/download the protocols and complete the short Feedback Form.

Have an update to share in the next GLB FHC newsletter? Email us!

Partner Spotlight: Trees in Peril Project

Eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana) are threatened by several non-native pests and pathogens. The Nature Conservancy (TNC), in partnership with USFS, is undertaking a three-year “Trees in Peril” project with public agencies, research institutions, and nonprofit partners to advance tree breeding programs and genetic research for five of the most imperiled tree species in the Northeast, including eastern and Carolina hemlock.


Identifying hemlock trees that remain healthy despite long-term exposure to hemlock woolly adelgid (Adelges tsugae) (HWA) and elongate hemlock scale (Fiorinia externa) (EHS) is a necessary step for advancing hemlock breeding programs. TNC and the New York State Hemlock Initiative at Cornell University (NYSHI) convened a working group in late 2022 to develop protocols for identifying and reporting lingering hemlock trees.


The working group developed two draft protocols: one to record lingering hemlock tree candidates in areas that have experienced high hemlock mortality (Lingering Hemlock Tree Search Protocol), and one to monitor conditions in areas where there is not-yet-significant HWA- or EHS-induced mortality (Hemlock Health Monitoring Plot Protocol). The draft protocols were shared with a variety of hemlock resistance stakeholders at a meeting organized by the Holden Arboretum on April 18. 

The working group is accepting feedback on the hemlock protocols through May 31! Visit this website to view/download the protocols and complete the short Feedback Form. The working group will be testing the protocols it has developed this spring and summer with the hope that they will be useful in identifying lingering hemlock in the years ahead.

Get Involved: Lingering Trees

In the upcoming quarter, the number one thing we need from our partners and allies is: Lingering Trees!

From mid-May to August is a great time to look for ash and beech bark disease resistant beech that are lingering in otherwise infected areas and may be resistant. It’s an enormous help to us to know where these trees are located! We work with our partners near each reported tree to get it incorporated into breeding programs.

Report tree sightings with the TreeSnap app or by emailing them to us directly at Training workshops to help with tree ID, using the TreeSnap app, and more are available online or in-person, with more to come in the future at other partner locations across the Great Lakes — contact us today to set one up for your organization!

Research Roundup
  • How BLD infection changes the physiology of beech leaves. Cameron McIntire from the USDA Forest Service quantified changes to leaf function and physiology in an infected stand in Connecticut. Compared to asymptomatic leaves, infected ones had reduced carbon assimilation, reduced instantaneous water use efficiency, increased dark respiration, increased leaf water content, and more. [McIntire 2023 Frontiers in Forests and Global Change]
  • Infection with beech leaf disease hurts colonization by fungal root mutualists. Researchers from the Holden Arboretum examined colonization by ectomycorrhizal fungi across two seasons (spring, fall) and two tree provenances (Michigan, Maine). Beech trees with more severe BLD had far fewer fungal mutualists, especially in fall after the growing season. Bonus finding: The fungal communities of trees from Maine vs. Michigan stock were significantly different, despite the trees growing together at Holden. [Bashian-Victoroff et al. 2023 Journal of Fungi]
  • What trees can replace ash in flood-prone areas? Researchers put 18 species to the test. Survey says: Bald cypress, American elm, river birch could survive up to 15 weeks of wet feet. Eastern white cedar, red maple, tamarack, swamp white oak, swamp birch tolerated about six weeks of flooding. Black walnut and sugar maple preferred to stay dry. [Keller et al. 2023 Trees, Forests and People]
  • 500+ year-old eastern hemlocks in Nova Scotia. The Nova Scotia DNR(andR) put out a report on a recent stand analysis in the Maritimes. The two oldest trees they found were hemlocks, 532 and 533 years old. The stand is uneven aged, and seems to not have gone through full-stand replacement in hundreds of years. [Woudstra et al. 2023 Biodiversity Conservation and Forestry Technical Report Series]

Have new research to share in the next GLB FHC newsletter? Email us!

In the News

The Great Lakes Basin Forest Health Collaborative is an initiative co-sponsored by Holden Forests & Gardens and the USDA Forest Service, funded through the Great Lakes Restoration Initiative
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