|Restoring our Grandest Tree
A hundred years ago, majestic American elms lined the streets of our towns and canopied the commons. The Great Hurricane of 1938 decimated them. Then elm bark beetles, feasting on the wounded and rotting bark, proliferated -- carrying the spores of a fungus that had recently been introduced to North America by infected logs shipped from Europe: Dutch elm disease (DED).
Today only a few old elms remain. They survive either because dedicated tree care specialists remove diseased parts and inject the trees regularly with systemic fungicides (a time-consuming process) ... or because a tree is standing alone, isolated from infection via beetles or via the natural root grafts elms make with each other.
Other elm species are more resistant to DED and can reach the same dimensions -- 100 feet tall, 65 wide at the top -- but they dont have the characteristic graceful, tapered vase shape of _Ulmus americana_. However, breeding programs have now resulted in true American elms that are well worth planting.
The Middlesex Conservation District this year will offer a limited number of perhaps the best variety, Valley Forge, at their sale on April 22-24. (Pre-orders are due March 25; call (978) 692-9395 for a catalog or see <http://www.middlesexconservation.org/>.) These trees come from Acton grower Bruce Carley.
They prefer good moisture, but tolerate some drought -- as well as some salt and soil compaction. Could I replace our dead maple with one of these? Its 13 feet from the street, and 17 from the house. My main concern is whether an elm would get enough soil water in this constrained space. I could enrich the soil in a big hole when I plant it, but when the tree gets big it will have to rely on the native subsoil -- pure sand here.
I also have to consider the power lines across the street. Eventually it would tower over them, but on the way I dont want to have to butcher it.
Finally, can I handle the training? All elms need pruning when young, to develop a strong single trunk -- and Valley Forge has one additional requirement thats a little odd. Although when mature it grows straight and tall to the spreading top, the very young sapling has a tendency to curl over toward the ground, in what Carley calls a whip shape. I would need to stake as well as prune it for four or five years, until it gets past that.
|For more information
- Saving the American Elm - the site of Bruce Carley, who raised the 'Valley Forge' Elms which are being sold by the Middlesex Conservation District this spring.
- Harvard Yard Trees - "The American elm is the tree that defines Harvard Yard. Its presence in the Yard likely dates back to around the founding of the University in 1636. "
- 1938 Hurricane left mark on New England - gives sources for more information
- How and why storms are named, by Jack Williams at USA Today.com - organized naming of tropical storms began in 1950.
- Elm Bark Beetle, at U. Mass Extension Service's site for Landscape Nursery and Urban Forestry. How elm bark beetles spread Dutch elm disease.
- Dutch Elm Disease, at North Dakota state University's Extension Service site. A detailed guide for tree owners.
- Dutch Elm Disease, on Fungal Biology, by Jim Deacon, of Edinburgh University, a website to supplement his book of the same title.
- The American Elm and Dutch Elm Disease, by M. Hubbes,
Faculty of Forestry, University of Toronto. "The fact that the Asian elms show resistance towards DED led to the assumption that DED originated in Asia. Recent investigations place its origin in the Himalayas."