Since some years, I am really excited about Hannah Perner-Wilson aka Plusea's textile circuits. Fortunately, I could join her workshop during the Schmiede 2013 and applied her textile speaker to a lead of a plant. First experiment worked well with conductive thread, which kinda harmed the leaf structure. Therefore, we experimented with conductive ink, too. The result was much quiter noise.
For the DIY people, you can find information and tutorials here: