A rare Amazonian cactus called the moonflower has bloomed for what botanists believe is the first time in the UK. Experts at Cambridge University’s Botanic Garden kept a night watch throughout the week so that they did not miss the flowering of Selenicereus wittii – an event which usually begins at sunset and is over by sunrise. The moonflower actually bloomed earlier on Saturday afternoon at around 3pm, and the garden said it was 28cm (11 inches) long. The coveted flower produces a sweet-smelling scent that turns “rancid” after just two hours, as the plant begins to die. The plant is only found on the high waterline of the floodplain rainforests of the Amazon basin. A post on the garden’s Instagram feed said: “Oh it’s been worth the wait, what a beauty! Our moonflower has opened & the smell is divine – similar to gardenia & jasmine atm & it’ll change (we think) into rotten veg smelling later.” The plant spirals around tree trunks, and the coveted flower is about 3.6 metres in the air. This plant is believed to be the only specimen in the UK, and worldwide it is listed in only 13 botanic gardens. Alex Summers, glasshouse supervisor at the botanic garden, said he was “excited” to share the blooming of the cactus, which was streamed live online. “It’s very rare to have this plant in our collection and we believe this is the first time the moonflower has flowered in the UK,” he said. “I noticed the flattened stems, or pads, which swirl around the trunk of our water chestnut had sent out a flowerbud in late November – which was a lucky spot as it’s almost 12ft up in the air and could have so easily been missed.” He said it had only recently “increased radically in size”, indicating that flowering was imminent. He added that he loved the story of how British botanical artist Margaret Mee brought the plant to the attention of a wider audience. She first saw the moonflower in 1964 but had to wait until 1988 to see one in flower. Her painting of it is held by Royal Botanic Gardens in Kew, south-west London. Summers said the cactus is expected to flower most years from now on. Thousands of people around the world have been tuning in to a live stream of the rare cactus this week. The plant had been expected to bloom at about 9pm. But in comments on the live stream, the team said the blooming was happening “a bit earlier than expected”, and that they were “so excited”. They then brought forward a live Q&A on Facebook that had been planned for 9.30pm. There has been some confusion over the rarity of the flower, with members of the public reportedly claiming to have their own versions of the plant and sending photos to the botanic gardens. The team at CUBG published an article clarifying that “moonflower” was a name used for many different species of plant.