Controlling weeds in cotonester ground cover planting – The best cure is to spot treat the weeds with Round up weedkiller. We have done this several times by using an old washing up bottle on a cane at one end and a sponge at the other with a small pipe connecting the two. When touch the weeds with the sponge on the cane this applies the weed killer without touching the cotoneatser. If applied in the correct weather conditions it normally only takes two treatments. If you would like to email us your postcode an a rough idea of the area we would be happy to give you a price normally it not very expensive.