Weed, its not, feed it does.. Thats because it thrives when fed with those weeders and feeders. You would need a weed and grass killer or something that is not slective as to its killing power. 20% vinegar comes to mind as an organic option. It can be bought through Marshall Grain in Texas and elsewhere. Spraying all the foliage everywhere will bring the mint to its knees. If you want all vegitation killed off, there are some 'serious' total vegitation killers too, but use care, as they will also prevent any new plantings from growing in the same area for at least 6 months. A weed whacker can help some, but you need to get the roots too.