I get weary of folks using the term 'weed' and wanting to know the easiest way to kill them. All plants have validity. Some are native, some are invasive and have been inadvertently transplanted where they should not be, some are perhaps not as pretty as their cultivated cousins. They all still have a place on the planet.

@bonehead Deb, the image shows Verbena bonariensis...or that is what it looks to me. I was raised in that part of the planet where V.b is a native plant. ( near Buenos Aires). In my student years in agriculture, we used to find it growing wild in the ranges where cattle are raised. Now quite away from its original place I grow it and let it flower. It is by now a cultivated form; in my perception very elegant amongst my prairie flowers ( Heleniums, Agastaches, Echinaceas etc) .It adds a stiffness to counterbalance the other forms and topped by endless bloom in summer until the hard frosts. Its blue/purple colour is hard to find in my mixture and tends to accent the other late summer /fall colours. All of this just from a "weed".
Those farmlands with natural grasslands have been turned into soybean cropland. Many if not all are treated with Roundup pre-emergence weed killer. It is possible that in the future the original V.b. may reach an endangered status... Fortunately, someone in the past saw that plant on passing....didn't see it as a "weed"...got some seeds and by horticultural improvement found strains that are hardier and now all of the temperate gardeners can enjoy it.
Perhaps, the image is not of V.b. However my comments still hold true. I also wish a better world where there's a place for everyone and every living creature...even for those that because of my present ignorance I've yet to find a purpose of their existence.
Arturo