Think Slow to Hit Low
To hit low under a tree, set up like you have your wedge in your hand but use a 5 iron.
Your stance will be slightly open, the ball will be back in your stance and your weight toward the target. Make a 3/4 backswing, you're making a gentle swing action, like a soft pitch. Don't punch at the ball, let the club pitch the ball low- and slow- under the obstacle in front of you.