Tree Burls ó Causes and Value

Burls from a tree trunk can yield valuable material for custom craft work. Here's some info on what they are and why they appear. June 14, 2014

I was recently exploring a wooded area for trees with unusual and unique growth patterns that I can use to make projects from. I came across a tree with a very unusual growth area. The tree is about 18 inches in diameter, and appears healthy. It's not dead, and I can't see insect holes anywhere. About 12 feet above the ground the tree balloons out to about 36 inches in diameter, forming a big round area about the size of a large beach ball. Above the unusual growth, the tree is normal, all the way to the top. Do any of you have an idea what could have caused the tree to develop a weird ball shape? Could it be termites, carpenter ants, wood-boring beetles, or some other insect pest, or could it be the result of some type of tree disease, which temporarily affected the tree, causing the weird bulge but not killing the tree. Any responses will be appreciated.

Forum Responses
(Forestry Forum)
From contributor Z:
Does it look like a tumor? If so it's more than likely a burl. If it's sound, it's a valuable wood in the specialty market, turners love it. Most loggers will cut it out and let the termites have it.

From the original questioner:
What are the possible causes of the unusual burl I described above? How likely is it that the burl I described above is filled with irregular holes and gaps, or is it possible that the burl is completely solid? Anyone with experience working with burl growths, please respond. I'm hoping it's completely solid.

From contributor T:
I once saw a cherry tree being cut down by a homeowner. The trunk was about 18" in diameter and had what appeared to be a large burl on its side. The outgrowth was about the size of the trunk and about 3' long. The homeowner let me take it. I was sure it was a burl. I could not find a veneer mill to slice it but one guy was nice enough to spend a few minutes on the phone. After some discussion he said it probably was not a burl just an outgrowth caused by some unknown reason. I finally had it milled into turning stock on a Wood-Mizer. There were no voids and it yielded some nice turning stock with unremarkable grain.

From contributor A:
If I remember my forestry 101 correctly, at least in cherry, galls or burls are caused by bacteria, agrobacter spp, vectored by ovipositing wasps, which causes the strange growth pattern. Cherry is more prone to this than most other trees. I have one 1/3 acre lawn that I mow that has at least six cherry trees with galls/burls growing on it.

From contributor R:
It's most likely a burl and probably has a few small holes inside. They are usually easy to fill. I'm not sure what starts them but if you mill them as a part of the log you can see where they start radiating out like a fan - makes a real spectacular piece of furniture. Itís certainly worth milling. There is another type I have we call it a cabbage burl. It usually grows very smooth on the side of the tree and has no holes. It's grain appearance is the same as when you cut a cabbage in slices across the top, very rare. There is a burl in my area that is about six foot in diameter with the tree through the center and it has been used to support the house roof. The burl has been chainsawn to make up a circular bar top.

From contributor C:
I mill a lot of burls and sell them it depends a lot on species of tree what will be the outcome. Oak for instance is not normally worth the time but ash and cherry normally mill out solid. This not always the case as I recently milled a white oak log that was so full of burl that almost the entire log had it throughout and was solid with no bark inclusions. This was a 24" x10' or 60 cm x 2.5 m log.