Rhododendrons only feel comfortable in loose, humus-rich soil. This type of soil is formed in places where soil micro-organisms are very active. Mulching will increase this activity: the layer of mulching distributed over the surface represents "food" and will incite the micro-organisms to greater levels of activity. Various types of organic matter can be employed for mulching: peat, semi-decomposed leaf mould, fine wood shavings and grass clippings are all useful. Mulching should be carried out once a year, preferably in autumn. The mulching layer should be 3 cm (1 in) thick and should be spread on the soil in a circle corresponding to the spread of the crown of foliage.
Advantages of mulching: I can readily recommend this method care to every rhododendron enthusiast, as mulching produces new humus. Additionally, the soil will remain loose and porous, will stay moist longer and weeds will be suffocated at an early stage.