In the air quality directive (2008/EC/50), the EU has set two limit values for sulphur dioxide (SO2) for the protection of vegetation within the zones designated by member states: the SO2 annual mean value may not exceed 20 micrograms per cubic metre (µg/m3) and the SO2 mean value for the winter period (1 October to 31 March) may not exceed 20 micrograms per cubic metre (µg/m3).
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It will keep weeds away; protect the plants by keeping the soil cool; decrease evaporation and reduce soil compaction. Be creative and use materials like: pebbles, bark chippings, gravel, cocoa shells, decorative pine cones, marbles, broken crockery, grass clippings or leaf mould. But avoid mulching too close to the stems to avoid the plant rotting in winter.
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