Will Roundup Kill Cockleburs?

Don't know what else you want to kill, but cockleburs are extremely sensitive to glyphosate (Roundup).

What herbicide kills cockleburs?

Some effective herbicides for cockleburs include Flumetsulam and Metribuzin. Use the herbicides appropriately, following the directions on the bottle. Mow over the new plants as soon as they come up. Doing this repeatedly eventually kills the plant.

How do I get rid of cockleburs in my yard?

If a small area of the yard has been invaded with cocklebur, hand pulling and hoeing work well to remove the plant. Those methods work best when done before burs form so seeds aren't dispersed when handling plants. When hoeing, uproot the plant with the hoe and pull the whole plant out of the soil.