I am not completely sure of the name of this weed. I really do not think it is joint grass or pop weed, but people might call it that. When you pull the stem it separates from the lower stem and on and on. It is like a hollow straw. Dark green color. Diameter of the stem might be 3/16 inch possibility up to 1/4 inch. It is growing at the edge of the field and seems to be creeping in a foot or two each year. This is a no-till field that gets traditional herbicides including roundup, but it doesn't seem to slow this weed down. I think tillage or cultivation might kill it or at least slow it down. Probably has an underground root system. What do you call it and what will help stop it? Thanks.