Are you 100% sure about it? The character looks more-or-less as you described:
It is a musical, set in the middle ages, he turns into a tree (just a pity I can't find any video to show you...), and in the end a princess turns him back to normal...
If it's still not it, could you remember any more details?
It's "Halloween" (1994) from the "Holidays for Children" video series by Schlessinger Video Productions (now Schlessinger Media), hosted by Michael G. Keck: