As the first step to model THz radiation through vegetation, we propose an initial path-loss model. This model considers the effect of the absorption and scattering loss due to air molecules and leaves on THz radiations. The attenuation loss of leaves can be derived by the means of THz time-domain spectroscopy for different types of leaves. Furthermore, by considering the effect of the leaf density on the total path-loss, this model can be customized for a variety of plant species. The proposed path-loss model can be deployed in plant monitoring applications of electromagnetic nano-sensor networks, which will be highly sensitive and will operate in the THz band.