In the air quality directive (2008/EC/50), the EU has set a limit value for carbon monoxide (CO) for the protection of human health: the CO maximum daily 8-hour mean values may not exceed 10 milligrams per cubic metre (mg/m3).
EEA standard re-use policy: unless otherwise indicated, re-use of content on the EEA website for commercial or non-commercial purposes is permitted free of charge, provided that the source is acknowledged (http://www.eea.europa.eu/legal/copyright). Copyright holder: European Environment Agency (EEA).
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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