Oak Tree Diseases – Burls

warty-burlsBurls can happen on oak trees, usually white oaks. They are caused by the fungus phomopsis. Burls are large swellings on the limbs and trunk. Sometimes, they occur naturally over young buds. Truthfully, the biology of burls is not well known. They don’t always negatively affect a tree and can even add a bit of character or beauty to it.

For some reason, the cambial growth, whether it’s due to environment or infection, is hyper-stimulated. The tree’s growth hormones get disrupted when the metabolism of the tree is hijacked by some other organism like a virus, fungus or bacterium. A ball of extra bark is built. Burls can grow to a great size or they can remain rather small. The largest burls occur on Redwoods and can encircle the entire trunk.

Burls can be removed by pruning or surgery. They contort the grain of wood and are actually prized in some circles. Furniture makers love them because they can add a lot of character to their pieces. Trees can carry this tumor-like growth and still look healthy above and below the growth. Oak burls can often mill out defective burls with rot and holes. You will probably want to get rid of these.

Sometimes, people sell their burls to artists, furniture makers or wood workers for cash. However, oak burls usually need to be removed. The crown gall bacterium is responsible for many burls. It comes with a little extra DNA, called a plasmid, which infiltrates the tree’s genetics. It prompts the tree to make special amino acids and growth regulators to produce the burl. The burl is obviously the preferred habitat for the bacteria.

However, figuring out what causes a burl can be difficult. The bacteria or fungus that started it can be long gone by the time the burl is formed. Burls can occasionally be associated with dormant buds, but that doesn’t explain why they get formed. Truthfully, we can tell you if you have a burl once it’s formed and we can remove it for you. We can’t figure out what caused it and if you are going to get more of them.

Research has shown that, by doing the regular things to keep a tree healthy such as pruning, fertilizing and watering it, will prevent burls from growing. Cutting a burl off will not damage the tree. It’s like taking a benign growth or wart off your skin. Burls take a long time to form, sometimes as often as 30 – 40 years. The sooner you notice the burl, the sooner we can take action.

Give us a call at 512-341-8888 if you have a burl on your tree and want it removed. We are happy to help you.