Significance Plants with integrated electronics, e -Plants, have been presented recently. Up to now the devices and circuits have been manufactured in localized regions of the plant due to limited distribution of the organic electronic material. Here we demonstrate the synthesis and application of a conjugated oligomer that can be delivered in every part of the vascular tissue of a plant and cross through the veins into the apoplast of leaves. The oligomer polymerizes in vivo due to the physicochemical environment of the plant. We demonstrate long-range conducting wires and supercapacitors along the stem. Our findings open pathways for autonomous energy systems, distributed electronics, and new e -Plant device concepts manufactured in living plants.