Monitoring of weeds in an extensive green roof

Weeds may be a serious problem in extensive green roofs since they usually are very competitive with the cultivated plants, especially in the adverse conditions of the Mediterranean roofs. The monitoring of weed infestation on an extensive green roof with six flora species (Armeria maritima, Cerastium biebersteinii, Dianthus gratianopolitanus, Dianthus carthusianorum, Potentilla neumanniana, Thymus serpyllum) intercropped with Sedum album was carried out. The cultivated species influenced the weed invasion in relation to their soil covering and growing performances. Thymus serpyllum, Cerastium biebersteinii and Potentilla neumanniana were the least infested species, and are therefore worthy of consideration in the creation of Mediterranean green roofs in the perspective to reduce the maintenance costs.