The present invention provides transgenic cover crop plants which after harvest degrade the hemicellulose and cellulose therein to fermentable sugars which can further be fermented to ethanol or other products. In particular, the transgenic plants comprise cellulase, hemicellulase and optionally ligninase genes from microbes operably linked to a DNA encoding a signal peptide which targets the fusion polypeptide produced therefrom to an organelle of the plant, in particular, the chloroplasts. When the transgenic plants are harvested, the plants are ground to release the hemicellulase and cellulase which then degrade the hemicellulose and cellulose of the transgenic plants to produce the fermentable sugars.