It is not rare. It is hidden. The NZ Forest Truffle grows underground. No cap. No stem. No gills. The fruiting body is a lump. Brown. Wrinkled. The size of a pea or a walnut. It sits in the soil among beech roots. You cannot see it. You cannot smell it unless you dig. You cannot find it unless you know where to look. Foragers never find it. Trampers walk over it. Only animals find it. Rats. Possums. Ground-dwelling birds. They smell the truffle from metres away. They dig. They eat. They spread the spores. The truffle depends on them. The truffle existed before they arrived. It evolved with different animals. Moa. Extinct now. The truffle waits. It adapts slowly. The fungus is mycorrhizal. Alpova nothofagi forms a mutualism with southern beech roots. Nothofagus fusca. Nothofagus menziesii. Nothofagus solandri. The fungal hyphae wrap around root tips. They penetrate between cells. The tree provides sugars. The fungus provides water and nutrients. Phosphorus. Nitrogen. Trace elements. The exchange happens underground. Invisible. The truffle is the reproductive structure. The fungus invests energy in producing it. The spores must be dispersed. Animals eat the truffle. They defecate elsewhere. The fungus spreads. Without dispersers, the truffle rots in place. Spores never leave the parent mycelium. Habitat is the soil of mature southern beech forest. Not regenerating forest. Not beech edges. The interior. The truffle needs beech roots that are decades old. Young trees allocate energy to growth. Old trees allocate energy to roots. The fungus needs the roots. It needs the carbon. Truffles form in autumn. The soil is damp. The temperature is cool. Not cold. Not freezing. Beech forests at moderate altitudes. Three hundred to nine hundred metres. Too low and the forest is mixed. Too high and the beech is stunted. The truffle grows in the zone where beech dominates. That zone is wide. The truffle is wide. But hidden. Range across New Zealand matches the distribution of southern beech. North Island: Te Urewera, the central plateau, Tararua Range. South Island: Nelson, Marlborough Sounds, West Coast, Canterbury high country, Otago, Fiordland, Southland. Stewart Island beech forests also host it. Within this range, the truffle is continuous. Every mature beech forest likely contains it. No one has checked systematically. The only way to check is to dig. Digging destroys the truffle. Collectors in the 1970s dug transects. They found truffles in half the sites. The other half may also contain them. The transects were small. The truffles are patchy. Threats are indirect. Possums and rats are effective dispersers but also damage beech forest. Browsing reduces regeneration. Without young trees, the forest ages. The truffle needs old trees. It does not need young ones. An aging forest without recruitment will eventually die. The truffle dies with it. Climate change may shift beech distribution southward. The truffle can only move as fast as its host. The host moves slowly. The truffle moves more slowly. Spores travel in animal guts. Animals travel across landscapes. Fragmentation blocks movement. Roads. Farms. Towns. The truffle cannot cross pasture. The spores rot in the sun.