A "Wolfy" Aspen Tree

"Wolfy" aspen tree, Wet Mountains, Colorado

A "wolf tree" has nothing to do with Canis lupus. It is a tree that has grown larger and broader than normal for its kind.

A New England definition:

These trees are large individuals that have a large diameter trunk and a widely spreading crown. There is also a good chance that a wolf tree will have some or even extensive damage. This may be a large limb that has broken away from one side of the tree or the top being blown out, usually from a lightning strike.

Wolf trees are the result of having grown in an open area. In many cases these trees were once in or at the edge of an open field. Wolf trees were initially left when forest was cleared to create a pasture or they got their start in an existing pasture and somehow managed to remain despite their cleared surroundings. Since a wolf tree once grew free of competition with other trees they were able to grow wide, broad crowns.

A Michigan definition:

If you have ever seen a tree in the forest that seems out of place because it is much larger than the trees surrounding it, you may have seen a wolf tree. A wolf tree is defined as a tall forest tree with large girth and great, spreading branches. Wolf trees are usually surrounded by smaller trees, signifying that the tree was once the only tree in the area and that the smaller trees have grown up years after the wolf tree was established. 

The Rocky Mountain definition that I learned as a kid was closer to the first — a tree, typically a conifer, that grew alone, broad and bushy because it did not have to grow up and up in search of sunlight.

Dad, a forester, scorned them because they did not produce as many board feet of useful timber as they would have when growing in a denser stand.

On the other hand, once retired, he turned landscape painter and depicted a few wolf trees.

Range conservationists also will use the term: "The grass in that pasture is old and wolfy. It needs to be burned."