Iron fertilizer against moss in the lawn – what experts recommend. Iron deficiency is a popular starter for winter-weary lawns, especially in spring.
The product is well tolerated by the grass, but less so by the user. Gardener Peter Rasch warns on NDR television that you should literally stay away from the product, because iron (II) sulfate can release toxic sulfuric acid. If the iron fertilizer accidentally gets onto stone slabs, for example by spreading it on footwear, the product can leave unsightly rust stains that cannot be removed.