The suitability of municipal plant waste for anaerobic digestion was examined using 57 different herbaceous and non-herbaceous samples. Biochemical methane potential (BMP) and anaerobic biodegradability were related to the degree of lignification and crystallinity of cellulose. The BMP of herbaceous garden plants (332.7CH₄NLkgVS⁻¹) was high, although lower than that of energy crops (400–475CH₄NLkgVS⁻¹). Herbaceous wild plants from natural grassland contained most lignocelluloses, leading to relatively low BMP (214.0CH₄NLkgVS⁻¹). Non-herbaceous phytomass had a high degree of lignification and a high concentration of crystalline cellulose, but due to the content of non-woody parts with a low concentration of lignocellulose the BMP was relatively high, 199.9 and 172.0CH₄NLkgVS⁻¹ for hedge cuttings and woody cuttings, respectively. There were indications that a plant lignin concentration of 100gkgVS⁻¹ is the critical biodegradability point in anaerobic digestion of phytomass.