A burl is a strange-looking collection of tree cells, which are called callus tissue. Normally, callus tissue is formed by a tree in response to an environmental injury such as a pruning cut, disease, or insect damage. In forest settings, callus often arises from storm damage that has eroded away or deposited more soil around the tree’s trunk.
hernibs 
Interesting…Just another part of the forest 🌳🌲🌿
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