Mushroom maps · prediction
Porcini map
Herkkutatti, the porcini (Boletus edulis), known here more precisely as kuusiherkkutatti, the spruce porcini, seeks mature spruce forest on fertile heath: open canopy and edges rather than a plantation grown shut.
The map does not claim mushrooms are growing here right now. It colors, across the whole country, the forest stands where the porcini thrives, in other words where it is worth walking. The weather decides the harvest, and the app now says so: Painota sään ja kauden mukaan dims the layer where the species is out of season or where the rain has not come. The color still means terrain, not a crop.
What kind of forest the porcini seeks
- Trees
- Spruce dominance decides, birch supports. A pure pine stand is another species' terrain: see the pine porcini.
- Site type
- Lehtomainen kangas (rich heath forest) is best, tuore kangas (mesic heath forest) and lehto (herb-rich forest) nearly as good, kuivahko kangas (dryish heath forest) clearly weaker.
- Ground
- Kangasmaa (mineral-soil forest). Mire types are not this species' environment.
- Stand age
- Stands around 50 to 70 years old are best; older than that, the prediction declines and disappears around the age of 120.
- Season
- From late July to early October, peaking in August and September.
- Northern limit
- Boletes hold out farthest north: the prediction halves only around latitude 66 and does not disappear even in Lapland.
The bars say whether a species is worth looking for now in the southern, central or northern part of the country. The division is the Finnish Meteorological Institute's. How the season and the weather are worked out
How to read it
Canopy cover is this species' most important variable in the model: an open spruce stand, about half closed, beats a dense one. Forest edges, clearing margins and pathsides are therefore the first places to check.
Identification and cooking notes: herkkutatti at Martat (in Finnish).
What the prediction is computed from
The base is the multi-source national forest inventory map data (MVMI 2023) from Natural Resources Institute Finland: tree species shares, site fertility, mire type, stand age, volume and canopy cover in 16-meter cells across the whole country. Each row above is one factor in the model, and the factors are multiplied together, so one clearly wrong factor is enough to zero out a cell. Toward the north the prediction is damped according to observation counts from GBIF and Laji.fi, so that sparse recording in the north does not read as the species being absent. More: the mushroom maps and their limits.