We are sorry to hear about the staining that occurred after using Scotts Green Max Lawn Food. The iron in Green Max Lawn Food may stain as indicated on the back of the label. The quicker a stain removal process is begun, the more effective the process will be. Sunlight and water will help to fade the iron stains from the product on outdoor surfaces, but will not completely remove them. While not endorsed or guaranteed by Scotts, the following products have shown to be effective at removing iron stains from regular concrete and are registered for this use: -Singerman Laboratories Concrete Rust Remover (only available on-line at The Rust Store) -Goof Off Rust Stain Remover Outdoors -Super Iron Out Outdoor We suggest you refer to the product label before applying any product to an iron-stained surface. Before using any commercial cleaning products to remove stains, test a small area to make sure the cleaner itself does not cause damage. Most stain removal products work best with two applications. We want you to be confident in our products. For this reason, we offer a product guarantee to our consumers. At your earliest convenience please contact us to see what can be done. You may visit our contact page by clicking on the following link http://tinyurl.com/7ag7a3n