In this paper, we investigate possible means of communication between plants and machines. Plants are capable of sensing a variety of environmental information. In particular, Avocado trees have an apparent response to increasing drought levels. We read out two different communication channels: morphological changes (leaf inclination) and the electric potential of the stem (biopotential) using distance sensors and biopotential electrodes, respectively. Leaf inclination reliably triggers irrigation, whereas the changes of the biopotential indicate water uptake and can be used to automatically stop the irrigation. Hence, through systematic experiments we demonstrate that morphological changes and biopotentials provide suitable control signals for interfacing plants with machines, and open a possibility to exploit abilities of plants in robotic systems.