Silvopastoralism is an activity with multiple benefits from both the ecological and economical points of view. Besides the potential cash flow to landowners, it has multiple environmental advantages and it can even help to reduce fire hazard in woodland. This hazard reduction is due to cattle grazing, and for it to become effective, it is needed to move herds to the correct place at the correct time. Only knowing when and where shrubs and sward are ready for grazing it is possible to make an effective management of herd placement. In loco inspection of the terrain can be time and resource consuming, as large areas must be verified. An automated system to detect the presence of shrubs and sward can help to improve the management of herds. Since Wireless Sensor Networks (WSN) have spread in the last years and, are becoming very popular in agricultural applications, the objective of this work is to analyse the effect of vegetation in radio-frequency (RF) signals propagation, and use it to detect plants growth. Experiments showed that by measuring and analysing the attenuation in wireless links it is possible to detect plants growth. Besides providing the infrastructure to transmit data from field wireless sensors, the network itself can be used as the sensor.