Outhouses (I think this is what they are called)?

I have recently started redoing the garden at my house (I despise the arrangements made by the previous owner), and I have an abundance of what I have heard called "Outhouses" (large standing stalks with yellow flowers). These things are, in my opinion, hideous. They fall all over the place, and attract bugs and insects like no tomorrow. So, I spent the weekend removing them (originally, I just cut them at the stalk, since they were falling into my BBQ). Sadly, they appear to be spreading flowers, and I have been pulling the roots out all around the rest of the garden. Does anyone know of any way in which I can just plainly kill the root without having to dig up the rest of the garden just to get rid of them all? Thanks.
Outhouses (I think this is what they are called)?

FlowersBirthday FlowersSympathy FlowersDon't use salt it will leach into the other parts of your garden and kill things you don't want dead. Try Roundup but be careful to spray only on the hideous plants.
Reply:Never heard of this flower but Roundup will kill anything. Just be sure to spray when the wind is not blowing and don't get it on anything you don't want to kill. If the plants don't die within a few days, you can spray them with the full strength and it will kill them for sure.
Reply:saltacting resources