Q: A few weeks ago we found a vine-like growth under the bark of my old poplar tree, rest its soul. Did you have any thoughts about this?

A: They’re the rhizomorphs (spreading roots) of a fungus named Armillaria mellea. The fungus produces distinctive mushrooms, called honey mushrooms, when well established in a rotting tree or root.

These rhizomorphs allow the fungus to spread from tree to tree, mostly attacking weakened trees or those that have had soil piled up around the base.

see Honey Mushrooms