Wednesday, March 7, 2018

Fagus Grandifolia: Beech Gone Wild

american beech treeThe sturdy, long-lived and stately American beech, Fagus grandifolia, has been slowly dying out since 1920, when a tiny European insect pest was accidentally released on our shores. Because of this lethal but unhurried tragedy, many forest tracts across the Northeast are being choked out by too many beech trees.

That’s right, beech decline has led to a proliferation of beech so extreme that in some places it is a threat to the health of future forests. With apologies to all the bovine readers out there, this qualifies as an oxymoron, I’m pretty sure. The ultimate cause of this weird situation is the aforementioned pest, but the proximate cause is a bad case of hormones being out of whack.

Before making sense of all that, some background is in order. Beech is in the oak family, or you could say oaks (chestnuts, too) are in the beech family, Fagaceae. Historically, it was a dominant species in many climax, or long-term stable, forest communities in eastern North America. From mice to black bears, a host of wildlife used to depend — and to an extent still do — on the seeds of beech, a protein-rich, three-angled nut enclosed in a prickly case.

The long road to hormone imbalances and oxymorons began nearly a hundred years ago in Nova Scotia with the introduction of beech scale insects from Europe. These soft-bodied pests range in size from 0.5 to 1 mm, or in non-metric terms, crazy-small to wicked-small. It is impressive and horrifying how a microbe billions of times smaller than we are can lay us low in a hurry, or even kill us. Similarly, a tiny pest like hemlock adelgid or beech scale can bring down a tree a million times bigger just by inviting some family over.

The beech scale insect cannot fly, or even walk far, and is not much to look at. But when the wind or a bird brings it in contact with a beech trunk, it inserts its sharp, thin stylet into the phloem tissue, and takes a wee sip of tree juice. This does not sound like a big problem. And it might not be, were it not for certain fungi in the genus Nectria.

Decay fungi are critical to the formation of healthy soils, and they typically behave themselves. But when Nectria finds a bevy of beech scale insects drilling tiny holes everywhere, the temptation is too great. It takes advantage of the myriad wounds to invade the phloem, the juicy part of a tree, resulting in a small dead spot called a canker. As these cankers spread over large portions of the trunk, the tree declines and dies.

For protection, beech scale insects cover themselves with a white, woolly substance. The presence of white fuzz and/ or rough, slightly sunken cankers on a beech trunks are signs of this epidemic, often called beech bark disease (BBD). Fortunately, about 1% of beech trees are naturally resistant to BBD.

The reason for beech’s “boom” has to do with how it makes babies. Seedlings can sprout from its nuts, of course, but it can also clone itself by sending up root-sprout saplings. Trees which hold a dominant place in the canopy constantly put out growth inhibitor hormones to put the brakes on mass-production of beech babies. It does not want too much competition while it is in charge.

But when a mature tree bites the dust, whether cut by loggers or killed by Nectria-Canker-Beech-Scale-Yuck Complex, there is no longer any hormone control, and you have Beech Gone Wild.

Given that a tree’s root zone is about three times its branch length, every mature beech that dies results in a broad and populous mini-forest.

Dense beech thickets inhibit regeneration of other tree species. Yes, those sprouts are doomed eventually, but not before they shade out everything else. To foresters, anything that interferes with natural tree regeneration is a big concern. Hunters hate beech thickets because they obstruct view, especially when beech hold their leaves through the winter. And they make it hard for maple producers to run tubing, or even just get through the woods.

There are ways to manage excess beech, though. Peter Smallidge, NYS Extension Forester and Director of Cornell’s Arnot Teaching and Research Forest, has researched and written extensively on the topic. His articles can be found at or you can contact your local Cornell Cooperative Extension office for information.

Photo of American Beech Tree, courtesy Wikimedia user Marqqq.

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Paul Hetzler has been an ISA Certified Arborist since 1996. His work has appeared in the medical journal The Lancet, as well as Highlights for Children Magazine.You can read more of his work at or by picking up a copy of his book Shady Characters: Plant Vampires, Caterpillar Soup, Leprechaun Trees and Other Hilarities of the Natural World

11 Responses

  1. Paul says:

    Cool article. When I saw all that white stuff on the bark I always assumed it was some sort of fungal pathogen. Thanks for the info.

    It’s amazing how many clones you see shooting out of those stumps. Is it really a “clone” though? I understand it would be genetically identical but isn’t it really a shoot coming out of the “parent” rather than a “clone” of the parent (wether from a stump or root)? It’s basically the same tree regenerating? Isn’t it just veg

  2. Paul says:

    vegetative propagation of sorts? (sorry – hit send too fast!)

  3. Boreas says:

    I believed the author invoked a little bit of artistic license, Paul.

  4. Cerise says:

    The link at the end is kind of makes a loop – to blog post on Cornell forest connect and back to here. Searching ‘beech’ ‘beech thicket’ in Cornell forest connect does not give instant gratification re beech thicket maintenance. General search found this:

  5. Sorry about that–here is a link to the main page, which I tried just now.

  6. Mick Finn says:

    The stump sprouting (and root sprouting) is referred to as “Coppice”, or “Coppice with Standard”. The forests will turn into fields of shrubs if the problem isn’t solved. It’s a very aggressive growth that will out-compete saplings.

    Usually during a cutting of beech for management purposes, the feller / buncher has a nozzle and the operator would give the stump a squirt of herbicide from his controls. Private forest management does this all the time, otherwise you’d end up with a very poor quality forest.

    Let’s see what the Essex Chain tract looks like in 10 years. The last cutting in there was a “canopy release” beech cutting, but without herbicides.

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