Of all the trees in the forest, the Willow is the most often caught walking at night. If you listen carefully, you can often hear them mutter to themselves as you pass by.
The Willow is only sometimes directly malevolent to humans but, like all trees?, objects to the use of the axe. It can be dangerous when deliberately stalking someone, but it will also follow out of curiosity or investigating a trespasser. In these cases, looking back at it or making eye contact may provoke the willow. Interfering with a willow when it is out walking is particularly risky.
The original document is available at http://www.thereamid.com/tiki/Willow