It is important to regularly remove leaves, twigs and other organic material, either with a leaf blower / vacuum cleaner, a stiff brush or a rake. Larger objects such as branches must be removed manually. If moss appears in areas where there is not enough sunlight, an anti-moss treatment could be necessary, preferably applied during the spring and autumn. Use a bio-degradable product for this; never use acidic liquids or bleach as these chemicals could damage the fibres if applied in too high a concentration.