Do you know how hard it is to write a blog about a Hickory Burl without mentioning Burl Ives? It is near, no make that – it is impossible, because you can see that I just did it. Indeed, Mr. Ives made his living as a talented performer with a home-grown persona, but he has nothing to do with those cancerous growths found on trees. He was a round fellow whose shape somewhat resembled that of a typical tree burl, but that’s about it. It’s just a word association thing. Burl: Ives – American actor and singer who….blah, blah. No, you need to get past the guy behind the snowman on the “Rudolph the Red-nosed Reindeer” Television special and start thinking “tree” when the word burl pops up.
Let me show you what a tree burl looks like (see photo above). I found this example growing on a Pignut Hickory about 15 feet up on the trunk. The thing was oval shaped and about three feet by three and a half in dimension. I had to crane my neck to get a good look at it. Fortunately, the ground around the base of the tree was still covered with a heavy layer of snow, or else I would have been forced to note the poison ivy that covers the floor of this woodlot. This would have forced me to put the words “burl” and “ivy” in the same sentence and that would have ended this blog before it began. My mind would have wandered into a rendition of “Silver and Gold.” As it is, I am able to continue this discussion by saying that burls are more typically found on oak, ash, maple, walnuts, and the like, so this example was slightly unique in terms of species.
To describe a burl as a cancerous growth is to miss the point. Trees having this kind of woody mass are normally healthy in all other regards, so it doesn’t involve an agent which spreads into the rest of the trunk or branches. The growth is basically a benign wart, in other words. As a matter of fact, scientists are not really sure what actually causes burls to grow. Some believe injuries, insects, or perhaps fungi (or a not-so-fun guys), cause the tree to react much in the same way as a gall is formed. Others point to circumstantial evidence that genetics are involved – noting clusters of burl trees within the seed range of a large parent tree.
It is known that burl growth begins when a twig bud fails to develop normally. For some reason burl- bound buds forget how to form limb tissue and start producing hog-wild woody tissue. You could say that the growth is cancerous in nature without actually being cancerous. Burls are stems that continue to grow but do not elongate (you can thank Dr. Richard Barrans Jr. for that answer, by the way). The woody structure of a burl consists of a gnarly grain and contorted growth rings that are very different from the normal ring growth of the tree. Externally this pattern is expressed by a contorted version of the tree bark. You’ll note the unusual texture of this hickory burl when compared to the normal shaggy bark of the tree (see below). It looks like a lump of solidified cottage cheese or one of my early attempts at making a snickerdoodle cookie.
Burls, including hickory burls, are eagerly sought by woodworkers because of their unusual figuring. Since colonial times, bowls have been made out of these unique growths and artfully turned burl bowls are still being made by regional artists. Some examples can command hundreds of dollars on the craft market. Larger burls can be thinly sliced to produce an attractively marbled, and equally valuable, veneer for furniture making.
This hickory burl is safe from the bowl-maker because it grows on protected land and because it already has a hole in it. A view of the far side of this growth (see here) reveals a neat entrance hole punching through it. This opening may have started out as a woodpecker hole, but it probably serves as a Red Squirrel den for the time being. Over the years, the fashionable entrance hole has been maintained by constant chewing. Having a distinctive burlwood door frame must make this place the envy of the woodlot.