You put horseweed in the title but then horse heads in the actual post.
Horseweed is a weed that grows hideous and giant very quickly. Not edible but not dangerous. We get a lot of questions about it as it is such a common weed. That’s not what you have here, just in case anyone else gets confused.
I am not familliar with horse heads plant; looks like a some kind of philodendron? I am also not familiar with philodendron (lol) but the limited info I see suggests it should not be fed. Sounds like Chubbs is familiar with it so I’d go with his advice.