In 1994 a park ranger named David Noble abseiled into a gorge in the Blue Mountains, about 150 kilometres from Sydney, and found a tree nobody had seen alive: the Wollemi pine, whose pollen matches fossils from the middle of the age of dinosaurs. Fewer than a hundred adults grow wild, and where they grow is still kept secret, because one careless visitor could carry a disease in on their boots. So the people protecting it did two opposite things at once. They hid the wild trees, and they made the species as common as they could: they grew young trees from cuttings, auctioned the first ones at Sotheby’s in 2005, and now you can buy one at a garden centre. When the Black Summer fires reached the gorge in 2019, firefighters were lowered from helicopters to lay irrigation lines, sworn never to say where they had been. The trees survived. I like the arrangement: the most hidden place in a national park and an ordinary pot on somebody’s patio, keeping the same tree alive from both ends.