DAVID GRAYS Winter Grass Killer will control the growth of winter grass when used as per the label instructions. The product works by stunting the growth of the plant, particularly the germinating seed which will start coming up in Autumn (generally speaking). Having stunted/stopped the plant ́s growth, it can not spread/reproduce. Sustained treatment is required to control winter grass, and this product should not be used on Kikuyu lawns, but is OK for Buffalo and Couch lawns - but always consult the label before using the product. Winter Grass Killer product is sold as a fine powder which is mixed with water for application. Product must be watered-into the soil to be effective on germinating seed. Ideally applied around Mid-Autumn or as the climate gets colder and the days get shorter, and will be effective during the entire Autumn-Winter-Spring cycle.