Reddit pointed me to you and it looks like you may have the most in-depth horror movie knowledge base and knowledgeable fans, so I hope you will recognize this movie.
I only have brief scenes in memory. I watched it on broadcast TV in the late 70's or early 80's. The setting and fashions made me think it was made mid to late 70's. Outdoor scenes make me think far north-east US (Vermont to Maine), but it could also be the Ponderosa region of the western US.
All I can recall is that it was a movie about a young girl (early teen or pre-teen) and the villian was just a regular ol' tree. I want to say it was an evergreen tree. It stood maybe as tall as the eave of a house and no taller than a single story roof-peak.
The tree was never shown to move (other than a gentle breeze moving the branches) and it made no sounds, but it could change locations and was stalking the girl. Anytime the tree was shown, it was just a tree planted in the ground.
What was vivid in my memory is that at the end of the movie, the tree was covered by a rock slide and killed, or so we thought — there was a final scene where it showed the rock pile with a sprout sticking out of the rubble to let you know the tree still lived.
I've tried to search for this movie from time to time, but I've always come up empty.
It's not "The Guardian" from 1990, or "From Hell It Came" from the late 1950's. It was definitely pre-1983 as I remember watching it before I moved to Europe.
I wish I had more/better description and I hope it rings a bell with you or your fans.
HelpfulJones (wishing I could be more helpful)