Decaying matter shapes life in soil, but it can also create hostile zones for growing roots. Professor Jiří Friml of the Institute of Science and Technology Austria (ISTA) and international collaborators have now identified “saprotropism,” a root response that guides plants away from decaying plant-derived matter—but not animal-derived decay. The study, led by Yuzhou Zhang, Professor at Northwest A&F University in China and published in Science, reveals how roots adapt their growth direction by sensing local pH gradients around rot.