Information on Zelkova for bonsai. My new Zelkova has been growing for five years and trained for three. I'm managing to kill it within a matter of weeks. A few yellow leaves to start out, which I clipped because they were depressing. It then managed to look quite healthy up until a few days ago, when it started to form brown edges around the leaves. Too little sun and too much water are both possible causes. Apparently, Zelkovas are not indoor bonsai.