Through ground-based observations of the Earth's spectrum from California, satellite observations of clouds, and an atmospheric radiative transfer code, we have determined the temporal evolution of the vegetation signature of Earth to characterize one novel approach to this search. We obtained an excellent agreement between models and observations, and overall, we find the evolution of the red edge signal in the globally-averaged spectra to be weak, and only attributable to vegetation changes when the real land and cloud distributions for the day are known. We also show that this signature becomes prominent under certain Sun-Earth-Moon orbital geometries.