Plant science has never been more important. The growing and increasingly prosperous human population needs abundant safe and nutritious food, shelter, clothes, fibre, and renewable energy, and needs to address the problems generated by climate change, while preserving habitats. These global challenges can only be met in the context of a strong fundamental understanding of plant biology and ecology, and translation of this knowledge into field-based solutions. Plant science is beginning to address these grand challenges, but it is not clear that the full range of challenges facing plant science is known or has been assessed. What questions should the next generation of plant biologists be addressing? To start to answer this question we set out to compile a list of 100 important questions facing plant science research. We had three main goals. 1 We aimed to stimulate discussion amongst the plant science and related communities, and identify areas of research that would have a substantial impact. 2 We hoped to encourage plant scientists to think beyond the limits of their own sphere of research and consider the most important research that could possibly be carried out. 3 We sought to illustrate the importance and potential of plant science to the broader public. This paper addresses aims 1 and 2, but questions were selected with all three aims in mind. This is intended to be a starting point. Research priorities and challenges change continuously and unpredictably as new concerns and needs arise, and new knowledge is revealed, and it will be important to review and reassess this list in the future. Here we present, with brief explanations of their significance, our list of the important questions facing plant science research today.