I have rocks were put down years ago and we put some carbon cloth down but now there is enough dirt Weeds are growing on top will preenpr

Thank you for your inquiry! Yes, you can apply Preen Extended Control Weed Preventer to your rocks. Please be advised that erratic weed growth can occur and that Preen may cause a light yellowish-brownish staining to light colored rocks. If staining does occur, it will disappear with time with the weather elements. Make sure the rocks are thoroughly dry at the time of application, and then water well after application. Any existing weeds would need to be removed prior to apply this product.