What are these kinds of lumps on a tree trunk called?
I saw these lumps on a tree in a park near my house. What are they called?
Solution 1:
They are called burls:
a roundish warty outgrowth from the trunk, roots or branches of certain trees.
(Collins Dictionary)
Solution 2:
At least the more weird-looking ones are called gnarls.
gnarl: A knot in wood; a large or hard knot, or a protuberance with twisted grain, on a tree.
[Wiktionary]
The word knot may be used for a more prosaic protuberance:
knot: a [relatively] small hard area on a tree or piece of wood where a branch was joined to the tree
[Cambridge English Dictionary]