It's extremely solid, and I would think at least 15 lbs.
Previous answers are still unclear. It obviously curves downward. Is the hook 16" from the post or is the arm 16" long, and the hook will be closer to the post than 16"?
If by driven you mean screwed into a tree trunk, I suppose they would work so long as you use bigger screws then those supplied by Vigoro. If you mean hanging over a branch then NO! There are other hooks for that available.