This is a fairly common question I receive, usually accompanied by a picture similar to the one shown here. It’s a good question indeed, and it’s one that I would like to explore beyond a simple “Yes” or “No” answer (spoiler alert: the answer is “No”).
In my early mushrooming days, it was the chaga fungus that had me most excited (don’t get me wrong, I’m still bedazzled). I remember exploring the hardwood forests near Pittsburgh (not exactly an ideal habitat for chaga) in search of this medicinal marvel, and discovering what I thought were potential candidates. I’d perceive one far in the distance and immediately scurry to the spot. Standing under the darkened mass, hoping my search yielded success, I’d wonder, “Is this chaga?”
Rather, the abnormal growth that had myself (and countless others, judging by requests on identification forums) fooled was a tree burl resembling the one pictured above. Through the years, my mushrooming skills have improved to the point where no confusion remains on this matter. I have encountered chaga dozens of times during my hikes through the forests of Pennsylvania, I have harvested it on numerous occasions, and I use the fungus as part of my primary medicinal strategy.
Still, there are many individuals who may find it confusing to discern between the two, and I understand. They kinda-sorta look like one another.
To answer the original question proposed in this article’s title, I’d like to further explore the differences, both superficially and functionally, between tree burls and the chaga mushroom.
A burl is an outward growth on a tree usually attributed to environmental stress, whether it be physical trauma, an insect, fungus, or even pollutants. Burls can be made up of numerous buds that would typically develop into new shoots, but instead they remain dormant.
Whatever their true cause, burls are not inherently detrimental to the tree. Rather, as trees mature, so do their burls, which develop beautiful patterns and colors that are prized by furniture makers and wood turners.
Unfortunately, burl poaching is a common practice especially in the old growth redwood forests, where burls are illegally harvested and sold for large profits. Harvesting burls from living trees can leave the trees more susceptible to infection and disease, though in many cases the tress are able to heal themselves.
It’s important to understand that a burl is not a fungus, while chaga is. A burl is simply an outgrowth of the tree, meaning the tree’s bark extends to include the burl. The two are not necessarily separate entities.
While the colors may vary depending on the species, burls are usually the same color, if not a bit darker, than the color of its tree. Contrast this to chaga, which usually forms as a blackened crust (on its outside), and appears as a distinct entity on its host tree.
While burls can form on numerous tree species, I encounter them most frequently on oak trees (Quercus spp.) in Western Pennsylvania.
Chaga (Inonotus obliquus)
Upon first glance, it’s hard to imagine that this fungus would serve any purpose in benefiting human health. Centuries of traditional use and current research, however, suppress that skepticism, if only by a little.
Chaga is a sterile fungal body usually found on birch trees, though also rarely found on elm, beech, and hornbeam. Its outer material is usually black, brittle, and cracked, while its interior is golden-orange and cork-like.
Chaga forms over several years within the tree and eventually erupts through the bark, pushing itself out from within. Thus, it is a distinct species from its host tree, and appears as such.
To distinguish chaga from a tree burl, ask yourself these questions:
- Is this the right ecosystem for chaga? Chaga usually grows in the circumpolar boreal deciduous forests.
- On which tree is it growing? Chaga grows almost exclusively on birch, though as stated previously, it has been found rarely on elm, beech, and hornbeam.
- What color is it? The outer surface of chaga is cracked, brittle, and relatively black (if not rather dark). A tree burl’s color resembles its host tree, perhaps a bit darker.
- What color is the interior? I don’t recommend haphazardly damaging formations on trees, though sometimes the interior color can be seen naturally without any effort, or simply by removing a small piece by hand. The interior of chaga is an unmistakable golden-orange color (see image below).
- Does the specimen appear to be a separate species, distinct from its host tree? If so, it may be chaga. If the specimen appears to be an extension of the tree, bark and all, you may be looking at a burl.
- Is the growth phallic in nature, or rounded? Chaga usually grows as a phallic, cone-like extension. Tree burls are generally rounded outgrowths. These are shape generalizations for both, as appearances can vary widely, though the majority of chaga fungi and tree burls I’ve seen fit these characteristics.
Having run through these questions, you can feel more confident in your identification of the chaga fungus. If you still harbor some confusion, feel free to send me a photograph and description of your unknown specimen, and I will be happy to assist in identification.
And oh yes, one final note: chaga fungi and tree burls are remarkable sights to view in nature, though both are prone to over-harvesting. Medicine can be made from chaga, and intricate woodwork can be produced from burls. If harvesting either, do so with the utmost intention while inflicting the least amount of harm. It makes the world a better place for everyone!
Thanks for reading, and as always … happy foraging!
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