Spring is in full flow in Kew Gardens, as a carpet of bluebells brings visitors into the woodland areas. But not all bluebells are equally welcome, and at Wakehurst, RBG Kew's wild botanic garden in Sussex, Iain is on a mission to hunt down the Spanish bluebell, which threatens our native species. It's a time for new beginnings, particularly for the lucky few on the prestigious diploma course. Like previous alumnus Alan Titchmarsh, these students could become tomorrow's horticultural megastars, such as Anna, who's creating intricate plant supports in the Woodland Garden, or Rob, who's working with endangered species in the Tropical Nursery. That's if they survive the traditional student clog and apron race! Out in the gardens, we see a pair of trees suffering from fatal storm damage and an aggressive fungus. Can Kevin find the perfect paired replacements for a vista that has UNESCO World Heritage status? We then go behind the scenes to meet Fran and Jenny, who use old skills and new tech to ensure there's a next generation of trees for Kevin to choose from. But the tree gang are foiled in their plans by a pair of ducks. It's an exciting time for Carlos in the Temperate House, as he nurtures a rare amaryllis that looks like it's going to flower for the first time after 10 years of care and attention. If it does, this will allow Carlos to pollinate it by hand, ensuring the survival of future generations. We go on the beat with Kew's very own constabulary, one of the smallest police services in the world, and reveal its 180-year history. We also dig into Kew's compost, with the arrival of tonnes of manure with a royal connection. Then, back at Wakehurst, we meet the Kew scientists using the latest drones and 3D modelling technology to help the government combat climate change with the power of plants.