What sets and constrains the size and form of organisms is still, by large, an open question. During this talk aimed at a broad audience, I will illustrate how are addressing this question regarding plant morphogenesis, from the viewpoints of solid and fluid mechanics. Firstly, we developed indentation-based measurements of cell internal pressure, which gave support to an analogy between plant tissues and liquid foams. Secondly, we are using microfluidics to quantify how tissue mechanical and hydraulic properties change when a plant starts growing. Thirdly, we are investigating how the hydrodynamics of droplet bouncing constrains the shape of organs involved in plant dispersal.