Ordinary cashew trees behave like ordinary trees. They send a trunk skyward and hold their branches aloft. This one carries two genetic anomalies, and together they changed the arithmetic entirely. The first is that its branches grow outward rather than upward, sprawling nearly horizontally instead of lifting. The second is that when a branch finally sags far enough to touch soil, it puts down roots and starts growing again as a new trunk. Neither mutation is useful on its own. Combined, they turn a tree into a slow-motion machine for occupying ground: reach out, touch down, root, reach out again. Repeat for ten centuries. The roots run about ten metres deep. Somewhere near the middle is the original trunk, though it is now effectively impossible to pick out from its own descendants.

Estimates of the canopy's footprint range from about 7,300 to 8,400 square metres, with Brazilian sources commonly citing roughly 8,500. That is somewhere between one and a half and two acres of shade thrown by one organism. The perimeter of the branch spread runs to about 500 metres — a walk of five or six minutes just to circle the outside. By volume of wood and leaf it is reckoned to equal about seventy cashew trees of normal size. It is also, emphatically, a working tree rather than a monument: it fruits, heavily, producing tens of thousands of cashews in a season, on the order of two and a half tonnes.

Local tradition credits the planting to a fisherman named Luís Inácio de Oliveira, who is said to have put the seed in the ground in 1888 and who, the story goes, died at ninety-three in the shade of what he had planted. The date sits awkwardly against a tree estimated from its growth characteristics to be more than a millennium old, and the two accounts cannot both be right — but the folk version has stuck, and it is worth knowing as folklore rather than botany. National attention came later. In 1955 the magazine *O Cruzeiro* photographed the sprawl and nicknamed it *O Polvo* — the Octopus — which remains the single most accurate two-word description anyone has managed. In 1994 the tree entered the Guinness Book of Records.

Superlatives invite challengers. Flávio Nogueira Jr., a state tourism secretary for neighbouring Piauí, has argued that a cashew tree in the municipality of Cajueiro da Praia is bigger, putting its footprint at 8,800 square metres — a figure attributed to study by a laboratory at the State University of Piauí. The dispute has the flavour of a friendly interstate feud, and it is unresolved. What is not in dispute is that both trees are doing the same strange thing, which suggests the Pirangi mutations are not quite as freakish as they look, and that somewhere in the coastal northeast the cashew occasionally decides to become a forest instead of a tree.

A viewing platform lets you see the canopy whole, and the aerial view is what sells the postcards. But the platform is not where the tree becomes comprehensible. That happens at ground level, in the green half-light beneath, walking between trunks of visibly different ages while trying to trace which limb came from where. Scale is difficult to feel from above and unmistakable from below. Visitors have been coming for decades, and the tree has absorbed them the way it absorbs everything else: slowly, without apparent notice, and while continuing to grow outward in every direction.