These trees are clearly malicious so you decide to get rid of them. Days later, you're covered in ash and oily goop.
A massive flock of little byrd spirits rise from the slain trees and drop a small box at your feet. “Thank you for freeing us from those trees... cheep cheep!”
You should really sleep more.
REST
All this adventuring has left you exhausted, and despite the oddities, you decide to sleep.
You toss and turn as the fire roars and crackles through the night. The disgusting trees give off a wretched scent from their pitch-black sap.