Slope vegetation is currently finding wide applications all over the world to mitigate erosive phenomena and improve slope stability. An innovative natural technology for slope protection has been recently developed in Italy; this uses only natural perennial grass plants with deep roots and allows operating in areas where climatic conditions were, until a few years ago, considered prohibitive for the development of vegetation. Such technology appears promising with regard to shallow slope instability; the plant roots induce mechanical and hydraulic effects on slope equilibrium, which typically increase the soil shear strength. The mechanical effects of vegetation result from the root/soil interaction processes, while the hydraulic effects derive from the significant reduction of water content enhanced by plant transpiration. The quantitative evaluation of the mechanical effect has been modelled and implemented in a computing algorithm.