Watch for unusual burls in Sisters Country forests

As with life, hiking isn't necessarily about the destination. It's about what you experience along the way.

On several recent hikes, I've noticed a variety of tree burls and decided to look into the phenomenon a little more closely. Burls are peculiar growths on tree trunks, branches, and roots. Usually, burls have a bulbous appearance and may appear simply as unobtrusive bumps. In other cases, they can become large, misshapen tumor-like protuberances larger than the tree trunk itself.

Burls are formed when something causes the cambium, the tree's growth layer on the inside of the bark, to run amok; but very little research has been done on the topic.

Most scientists believe that some form of environmental stress is the trigger for the peculiar growth pattern. Among the most commonly suggested causes of these interesting irregularities are insect or fungus infestations.

However, one study from the Institute of Northern Forestry in Fairbanks, Alaska, observed that trees at higher elevations, near timberline, seemed more prone to burl formation. Trees on north-facing slopes with less sunlight and colder temperatures were also reported to be more burl-prone.

Burls are fairly common in the Sisters area and can be found on different tree species and at varying elevations. Anecdotal evidence from the local area could be seen as consistent with the Alaskan observations, since burls often appear to be more prevalent in denser, stressed tree stands at higher elevations.

Most trees are able to survive just fine with the deformities, and bark covers over what might otherwise appear to be a wound. Some fire-killed trees in the nearby B & B burn offer a unique chance to observe burls with the bark peeled away.

The Alaska study also found some uniformity in the timing of burl occurrence on individual trees, with growth of multiple burls often beginning simultaneously. The study also suggested further examination of a possible parallel of the trees' "deviant growth processes" to cancer in humans.

Quite a few burls can be seen locally on firs along the Pacific Crest Trail (PCT) near McKenzie Pass. The PCT is a 2,650-mile trail from Mexico to Canada. 430 of those miles are in Oregon, and there are some great access points to the trail right here in the Sisters area. One of those accesses, however, the McKenzie Pass Road (Highway 242), will be closed much of this year; although it is expected to be open from our east side during much of August.

Burls also occur on tree branches, and many examples can be found in the Big Lake and Patjens Lake areas near Santiam Pass. In cross section, the wood grain of burls can be quite beautiful. Large burls are often used in furniture and wood sculpture.

Burls are fairly common in the Pacific Northwest. Redwood burls are a marketed oddity in southwest Oregon and northwest California, and some of the largest burls in the world are found in British Columbia.

Since burls do not seem to cause great harm to trees, forestry experts discourage attempts to remove them, since the resulting wounds to a tree would be more likely to cause damage than the burls themselves.