Mulch II.
Gravel and grit - alpine plants are small and slow-growing and must have a well-drained soil to grow well in a rock garden. By applying a thin layer of coarse gravel or grit around them, not only are competitive weed numbers kept under control, but the soil drainage is improved and rotting avoided because harmful winter rains quickly run through it.
Pebbles - large pebbles create strong visual impact on the surface of containers while reducing water loss. They also ensure that the dusty surface of the compost will remain undisturbed if pots are sited by open windows.
Grass clippings - an excellent mulch available in the summer is grass clippings. These can be spread around plants or used to cover the odd gap on the soil surface and can be collected later and incorporated into the compost heap. It is less ornamental than cocoa shells, so use it at the back of borders where it won't be seen. It is great value as it is free, whether from your own lawn or a neighbour's. If weedkiller has been used on the lawn, then do not use the clippings for four cuts.