Most flowers sold in the florists and supermarkets of Europe are grown in East Africa, where the warm climate supports roses and other plants to grow year round. But is it sustainable? Vivienne Nunis follows the international supply chain from a Kenyan flower farm to the hub of the global flower trade near Amsterdam, where every morning stems are sold at auction before being transported in cold storage trucks to buyers across Europe. The Dutch have been trading flowers since medieval times, when speculators paid enormous prices for tulip bulbs. We pay a visit to Amsterdam's Tulip Museum to find out why. The worldwide flower market is worth $40bn a year, but as growing numbers of consumers start to question the true environmental cost of what they buy, some growers are advocating for a return to seasonal, local blooms. We visit English grower Tess Wardman of Iris and Wilf flowers. Producer: Sarah Treanor. Image: Bouquets of roses for sale. Credit: BBC