Inside Kew’s tropical nursery – the secret greenhouse where the world’s rarest plant life begins

There’s a story that sums up how things work at Kew’s tropical nursery, and it involves David Attenborough, the RAF and a giant tortoise.

In the Eighties, the Café marron plant was thought to be extinct. But a schoolboy on the island of Rodrigues, Mauritius, took a piece of it and showed it to his teacher. Somewhat miraculously, she recognised it, and contact was made with the horticulturalists at Kew. A specimen was passed from RAF pilot to RAF pilot, eventually winding up in the labyrinthine collection of glasshouses that is the Tropical Nursery. After three decades, one of the staff had finally succeeded in encouraging the plant to seed. When it germinated, however, it didn’t look anything like the specimen that had made its way across the ocean. Staff wondered what they had done wrong.

The giant tortoise is the main predator of the Cafe marron (Ramosmania rodriguesi) – or, at least, it would be, if the plant hadn’t evolved to transform its leaves, from stringy and unappetising to fat and lush, only after it had grown taller than the tortoise’s reach. But it took David Attenborough, who worked with Kew’s horticulturalists on The Private Life of Plants, and his giant tortoise-owning friend, to prove the theory. The tortoises were presented with both types of leaf: juvenile, which they ignored, and developed, which they munched down on happily.

With the tortoise test as proof that those hard-won seeds did produce the right plant, Kew sent back 20 to their original habitat in Mauritius, where they continue to thrive. As for the giant tortoise? There are no more on the island, the plants won out.

This just one of shaggy dog stories that Lara Jewitt, Kew’s Nurseries Manager, tells as she shows me around the gardens’ tropical nursery. This is Kew’s biggest greenhouse, and its most secret. Instead of the swooning elegance offered by the Palm House or the sharp Eighties edges of the Princess of Wales conservatory, the Tropical Nursery is a fit-for-purpose collection of large glass boxes, shrouded from public eye by an unprepossessing fence.

But this is the beating, climate-controlled heart of Kew Gardens. It is here that the rarest plants in the world are brought from far-flung climes; mysterious specimens are gently coaxed into flower and seed over the course of decades and new plants are grown to fill the displays in the public glasshouses. This is where life begins.

On Sunday, Jewitt will show a handful of people be around the nursery as part of Open Garden Squares Weekend. This is one of 230 of the little-known gardens participating across the capital, which usually has their doors closed to the public.

Kew Gardens-Inside greenhouse

They, like me, will be bamboozled by the sheer scale of the nursery. There are 10,000 species under 6,500 square metres of glass, separated into four units: orchids, arid, temperate and moist. Those are then split up into different types, such as carniverous plants, ferns, water lilies.

There are six zones dedicated to orchids alone – it’s the world’s oldest and most comprehensive orchid collection – and they hold some which have been there for decades as staff figure out how to make them flower. One, known as The Queen, took nearly four decades to flower before it erupted with a 12ft blooming stem last year. “This is the luxury of Kew,” Jewitt explains. “Anywhere else, they wouldn’t give room to this plant, which hasn’t flowered in 40 years, which is now so big we can’t actually move it.”

Each of the different rooms has a different atmosphere, in part because of the controls that mean sprays of hot, damp air are puffed out every few minutes, but also because of the unique architecture that is built by thousands of different plants ushered into groups of their own kind. The dense, mist-laden foliage of the fern room feels a world away from the barren aridity created by hundreds of cacti lined up in rows.

It takes an expert’s eye to spot the extremely rare specimens, such as the world’s tiniest water lily. Discovered in the last decade in thermal springs in Rwanda, the Nymphaea thermarum now only exists in cultivated nurseries after the locals changed the flow of the water to wash their clothes in, destroying the plant’s habitat in the process. In 2014 one was stolen after being on display, probably, Jewitt says, “to order, for loads of money”. It was an unusual enough theft to appear on Crimewatch, but the nursery rule of always having three plants before one goes on display meant that the specimen wasn’t lost forever.

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