Bracken fern grows on hillsides, in clearings, along the edges of the bush. It is a pioneer, a coloniser, a fern that takes over after disturbance. But there was once a bracken fern that made today's plants look like seedlings. A fern with fronds that rose 3 metres from the ground, with a rhizome as thick as your arm, with groves that covered hectares of forest floor. It was the lost fern grove, and it is gone. Size and dominance made it special. A 3-metre fern is a giant. Its fronds were broad and triangular, forming a dense canopy that blocked the light from the forest floor. Its rhizome was massive, spreading metres through the soil, sending up new fronds at intervals. A single plant could cover a patch of forest the size of a house. It was the dominant ground cover of the lowland forest, the green carpet under the trees. It built the forest floor. The lost fern grove was a foundation species. Its dense fronds shaded the soil, keeping it cool and damp. Its thick rhizomes held the soil together, preventing erosion. Its fallen fronds added organic matter to the forest floor. It was the heart of the lowland forest understorey. Ferns reproduce by spores, released from the undersides of their fronds. The lost fern grove produced millions of spores, carried by the wind to new locations. It also spread by rhizomes, forming large, clonal colonies. That strategy works when the forest is stable. It fails when the forest is cleared and burned. Forest clearance and fire destroyed it. When Māori arrived, they cleared the lowland forests for gardens. They burned the undergrowth to encourage new growth for birds. The lost fern grove, which needed deep shade and undisturbed soil, could not survive in open, burned landscapes. When Europeans arrived, they cleared the forests for timber and pasture. They burned the remaining vegetation. The giant fern could not compete with grass. Its rhizomes were dug up by pigs. Its fronds were eaten by cattle. By the 1880s, it was gone. The last groves were probably burned by a farmer clearing land for a new paddock. No one knew they were the last. The smaller fern survived. The common bracken still grows on hillsides and in clearings – smaller, more adaptable, able to survive fire and grazing. It is the survivor, the one that kept its head down. But the lost fern grove is extinct. A few pressed specimens in a herbarium, a few spores in a core sample, and the memory of a fern that used to blanket the lowland forests. The floor phantom has faded. The understorey is not as deep as it used to be.