Sulphate of Iron is used for lawn improvement, moss control and for creating the acidic soils needed by lime-hating plants such as rhododendrons, azaleas, heathers etc. It darkens the lawn grasses and improves their appearance. Used regularly, it gradually increases the acidity of the soil, which discourages some weeds and favours the finer grasses. It helps to protect the lawn against some common diseases and controls moss and algae growth.
As it is soluble in water, a convenient "moss killer" can be made by dissolving 40 grams (1oz) in 10 litres (2 gallons) of water and applying this from a plastic watering can with a fine rose over 3.5 sq m (4 square yards) in spring and autumn. In spring, the inclusion of sulphate of ammonia 70g (2oz) will boost the growth of the grass but this should be omitted from the autumn treatment so that the grass will harden off for the winter.