In a development that should terrify anyone who has ever rolled their eyes at a friend's botanical Instagram habit, a casual social media post has led to the discovery of a new species of giant waterlily hidden in the Colombian jungle. The plant, which is so enormous it can be seen from space, is already considered critically endangered - because nothing says "rare botanical treasure" like "we found it just in time to watch it disappear."

Giant waterlilies, which can measure up to three metres across and support the weight of a small child, are among the oldest flowering plants still alive today. They predate the breakup of the continents and have been culturally relevant from the Egyptians to Monet, proving that even ancient plants can have a better PR team than most modern startups.

Three years ago, Carlos Magdalena, a world-renowned waterlily expert at the Royal Botanic Gardens, Kew, was scrolling through Instagram when he spotted a photo of someone swimming among several giant waterlilies in the Inírida River in Guainía, Colombia. Jeremiah Harris, who took the photo and runs a carnivorous plant nursery in the US, had no idea of its significance - he had mistakenly identified the waterlily as the more common Victoria amazonica. Magdalena, however, "immediately suspected" something was unusual, because the natural range of Victoria amazonica does not extend to the Inírida River. In other words, the plant equivalent of a wrong zip code turned out to be a whole new species.

Magdalena messaged Harris to track down the exact location and spent several years analysing satellite imagery and securing funds and permits to verify the waterlily for himself. Along with a team from the Jardín Botánico in Bogotá and members of local indigenous reserves, he embarked on a five-day expedition deep into the rainforest. After several days of exploring the flooded jungle with no luck, their driver advised them where to look. With only 10 hours left until their return flight, the team sailed overnight in total darkness to a small lake deep in the flooded rainforest, where they finally located a population of the waterlilies.

"It was so emotional I shed a tear, it was one of those moments that will remain with me for life," Magdalena said. "Coming across something like this is absolutely totally fascinating, it's jaw dropping." He added: "Giant waterlilies give away their secrets slowly. It's remarkable. We believe we know everything but the reality is we don't, there's lots of things still to be discovered and protected."

The team collected material for formal identification, and a paper published Friday in the journal Phytotaxa confirmed it as a new species to science. The waterlily has been officially named Victoria colombiana. There are just three other known giant waterlilies, making this a very exclusive club that nevertheless cannot be bothered to return your calls.

Harris, an author of the study, said his friends always teased him for taking selfies with plants, but the fact this one ended in the discovery of a new species was "incredible." "I was just so excited, absolutely elated," he said. Magdalena noted: "This is one of those extraordinary stories where indigenous and horticultural knowledge with the help of social media and technology came together to uncover a truly extraordinary botanical achievement."

The team estimates there are between 30 and 50 Victoria colombiana waterlilies in the wild, making them extremely rare and at risk of extinction. Maarten Christenhusz, a plant taxonomist who analysed the sample, said new species are found all the time, but few are as "large, spectacular and emblematic as this one. This new giant waterlily can even be seen from space, which is a striking reminder of how much we still don't know about life on our planet."

The team is working towards an official International Union for Conservation of Nature (IUCN) Red List designation. Efforts are also under way to support long-term conservation, including the possibility of establishing a naturalised population in a more accessible lake within indigenous territory. Researchers hope to continue collecting the plant's seed with the aim of cultivating it in Bogotá. If successful, there is a chance the waterlily may be grown at Kew Gardens - because if there's one thing a giant waterlily needs, it's a British postcode.