This stuff grows wild in our yard and seems to be impossible to kill. I thought it might be something to transplant around one side of the chicken run for shade but I don't know if it's safe for them to eat if it goes inside the pen. DH calls it grapevine but there are no grapes or flowers or anything on it. But it looks just like a grapevine and has the tendrils that hang onto anything in their path. Any idea what it is?