It's early spring in Kew Gardens and daffodils, crocuses and magnolia are bringing out the visitors in search of the first colour of the year. Also making a fresh start is Simon, the new head of living collections, and he's got the massive job of evaluating nearly 17,000 different plant species in the gardens to decide what stays and what goes. Meanwhile, Paul is doing a health check on the tuber of a dormant titan arum, a perennially popular plant that produces a huge flower that smells of rotting flesh. Kevin is also embracing change as he takes over as Kew's chief tree guardian, head of the arboretum. He's using sophisticated technology to see what is happening inside some sickly trees… that is, if the £5,000 computerised sonic hammer behaves itself. The 10-storey royal pagoda reopens for the spring season, and we get a guided tour with Rachel from Historic Royal Palaces. She tells us all about its history, from being a playground for Princess Augusta in the 1700s, through being used for testing bombs in World War II, to the cutting-edge restoration that has returned dragons to its rooftop and the whole structure to its former glory. Alberto shows us spring in the glasshouses, and we see the unusual emperor alcantarea go out in a blaze of glory. It grows two metres in two weeks and then produces strange spikey flowers for the first time in its 20-year life — but this is the last thing it does before dying. Meanwhile, at Kew's sister site Wakehurst, conservation supervisor Steven is keeping ancient skills alive: he's coppicing the trees and using the wood to create hedgerows. Leaping into the 21st century, Chris is making a withdrawal from Wakehurst's high-tech Millennium Seed Bank. He is thawing deepfrozen seeds for Alice in the nursery, who brings them back to life and takes the resulting coastal plants down to the Brighton seafront as part of a multimillion-pound effort to return lost plant life to the area.

Summer is rolling into Kew Gardens, and the giant waterlilies are once again drawing the crowds, who come to marvel at their size. This year, Carlos and Lucy think they've discovered a new third species of giant waterlily previously unknown to science. We follow them as they gather the evidence, along with partners in Bolivia, to try and prove their discovery to the world, and also see how Brie handles the monster-sized lily pads, when they take over the Waterlily House. Aaron is looking at ways to replace coffee plants threatened with extinction by climate change, pests and disease. With the future of our favourite beverage in his hands, we follow Aaron from the labs at Kew to the plantations of Uganda, and onto a coffee roaster in Bristol to find the perfect new brew. The stakes are high: if Aaron fails, it could mean no more coffee for any of us. We also find out from garden and plant historian Advolly how Kew had previously helped with a Victorian coffee crisis, and how Kew's first plant collector of colour played an integral part in the story. Down at Kew's wild botanic garden Wakehurst, Katie and the tree gang have to deal with some invasive rhododendrons that are threatening the plant collection, and it'll require abseiling with chainsaws to get to those hard-to-reach places. But not all rhododendrons are so unwelcome, and Olivia shows us their world-beating collection. We then learn about the Kew course that attempts to change the face of 21st-century horticulture and meet some of the inaugural students. In the Palm House, Florence overcomes her fear of heights to do some pruning in the roof and, back at ground level, Steph is refreshing the Alpine House plants ready for this year's summer rush.