Help! Need Weedkiller advice!!!

Help! Need Weedkiller advice!!!

Hey guys, I need some advice, BAD! I live in the country and have 2 horses. During the summer, the plan was to have them graze on the grass in a 2 acre pasture, but it is over run with goldenrod (which I found out is a perennial, so it explains why it came back). I need to kill it so the horses can use it, but I dont want to have to put down toxic weed killer!!! We have a well so that is part of it. I also have wild blackberry bushes back there that I don't want to kill, but it's not as important to have them survivive. SO anyone know of a weed killer which is less toxic and widely available?? Thanks!!
Our Little Apartment

Our Little Apartment

*new girl who used to be here and left and came back*

*new girl who used to be here and left and came back*

Growth

Growth

ID help

ID help

Purple Tree

Purple Tree

John Wang – a camellia hybridizer living in San Francisco Bay Area

John Wang – a camellia hybridizer living in San Francisco Bay Area