The Giant African Mahogany

In the wild, Khaya senegalensis stops at around 30 to 35 metres. This one is 49.1 metres, which makes it the tallest tree in the Jardim Botânico's living collection and roughly the height of a sixteen-storey building. It is a West African tree, from the Sahel and the dry savannas, and it has done considerably better in Rio than it manages at home. The garden made it the anchor of its Trilha das Árvores Gigantes, the Giant Trees Trail, opened on 21 September 2022, which is Brazil's Tree Day. Marcus Nadruz, who coordinates the garden's living collection, led the first walk. The trail takes in ten or eleven specimens depending on which report you read, every one of them over 25 metres, and the runner-up is an imperial palm at 48.1 metres, a metre short. What nobody has published is how old it is or how thick. The garden's own trail page sits behind a login, so any measurements it holds are unreadable from outside, and the two news reports of the launch give the height and nothing else. If you have walked the trail with a guide who knows the rest, we would like to hear it. The height on its own is worth the walk. Standing under a mahogany half again as tall as its species manages in Africa is a strange piece of arithmetic to do with your neck.