To provide a vegetation base material for reproducing a quasi forest soil layer on an artificial slope through setting a to-be-decomposed layer containing wood slices and a decomposition promoting layer containing nitrogen on the vegetation base material and decomposing the wood slices at an early stage.

This vegetation base material 10 has a net 26 having a cylindrical material holding part 30 and a vegetation material 32 held in the material holding part. The vegetation material has the to-be-decomposed layer 36 containing wood slices 34 subjected to heat treatment (steam heating or boiling heating) in the presence of water, and the decomposition promoting layer 38 containing nitrogen fertilizer 42 and arranged near the to-be-decomposed layer.