HI Mirth, I like your idea of a grounding rod. Never thought of that.
I took heavy PVC conduit, cut it to 8", secured it to the fence post and just dropped the metal conduit into it. That way, if or when I want to take the metal conduit down during harvest, I just untie the clothesline on the ground, lift the tube out of the holder and drop the vine to the ground or lean it on the fence to harvest.