To be effective, the weedkilling and mosskilling ingredients need time to work. For best results they need to stay put for 48 hours. If the granules are washed off before 48 hours is up – either by rain or by you watering them in – you may find that some moss and weeds remain. The exception to this is J Arthur Bower’s Lawn feed, which can be watered in straightaway if it’s more convenient for you or if no rain is forecast. Water gently with a hose – you don’t need to use a huge amount of water.