As a girl, Caroline Dean would watch the cherry trees in her childhood garden unfurl their pink and white blossom and wonder how it was that they all flowered at exactly the same time. She tells Jim Al-Khalili that the flowering synchronicity she observed was to spark a life-long fascination with the timing mechanisms of plant reproduction, in particular with a process called vernalisation - how plants respond to extreme cold. Professor Dame Caroline Dean of the John Innes Centre in Norwich has focussed right down to the molecular level, homing in on the individual cells and genes that flip the flowering switch. For thirty years running her own lab Caroline has been asking (and answering) questions like why some plants need a period of cold before they can flower the following Spring, how plants know that the cold winter is really over and it's safe to flower and, when winter is so different around the globe, how do plants adapt? Her team focused in on one gene - with the snappy title of Flowering Locus C or FLC - and by delving into the world of epigenetic regulation, they uncovered the processes by which this gene was slowly turned off over winter, enabling the plant to flower the following spring. These ground-breaking discoveries have profound implications for human health and for food security. As Caroline tells Jim, the cellular memory system behind a plant gene flicked to the "off" position, is very similar to the switching and expression of genes that cause diseases like cancer in the human body. And as the climate warms and fluctuating temperatures affect our seasons, her work will deepen understanding of the molecular basis for flowering times - vital for farmers and plant breeders to adapt and protect our food supply. Producer: Fiona Hill.