Tattis.Tattis — the mushroom forecast that shows the right forest and the right moment.

Tattis's heatmap combines three factors: a habitat model for the species, daily weather conditions, and the time of year.

• Habitat (stable): each species has its own model trained to predict the suitability of a location. The model uses forest type, tree cover, soil, elevation and vegetation indices, plus thousands of observations from laji.fi.
• Weather (updated daily): from the Finnish Meteorological Institute's open data, we calculate for each species whether the past few weeks of rain, temperature and night frosts support fruiting body growth right now.
• Season: every species has its own growing season. Outside that window, the forecast drops to zero.

The product of these three factors sets the map colour: pale yellow means low probability, deep red means high probability.

Tattis tells you where and when mushrooms are most likely to appear, but it doesn't guarantee it.

• The forecast is statistical. Weather stations are sparsely distributed, forest inventory updates with a lag, and local conditions vary with tree cover, slope and microclimate.
• The map guides — it doesn't find. Red and orange shades mean an area is potentially suitable in the current conditions — not that there are mushrooms there right now.
• Always identify each mushroom yourself. Edible species have toxic look-alikes. If you're not absolutely sure, leave the mushroom in the forest.

Use Tattis as a tool for trip planning and choosing where to go. Trust your eyes, your hands and your field guide when you actually pick. When in doubt, ask experienced foragers — for example the Finnish Mycological Society's Facebook group.

Yes, the basics of Tattis are free. The free version includes:

• Search and the 19 edible species recommended by the Finnish Food Authority
• Marking your own mushroom spots and notes
• When signed in, cloud sync of your observations and submission to laji.fi

A Pro pass unlocks the full app.

Pricing:

• Month €2
• Year €10
• Lifetime €50 (one-time)

Pro features:

• All 32 species — including ones outside the Finnish Food Authority list, like the spring agaric and other rarer treats
• Mushroom heatmaps — species-specific probability visualisations for the whole of Finland
• Forest-type maps — groves, heathland and other Luke forest categories
• Nature reserves — boundaries on the map so you know where you can roam and pick
• Species-specific weather — regional conditions (e.g. Pirkanmaa, Uusimaa) for your area, not a country-wide average
• Offline maps — MBTiles downloads to your phone with lightweight delta sync; works without a signal
• Push notifications — get an alert when conditions for your favourite species turn favourable in your region
• All future AI features at no extra cost

Payments are handled directly via the App Store or Google Play, using your preferred payment method.

There's nothing to cancel — all Tattis Pro purchases are one-time passes, not recurring subscriptions.

• Month (one-month pass): expires automatically after a month. The app does not charge you again on its own.
• Year (season pass): expires automatically after a year. The app does not charge you again on its own.
• Lifetime: a one-time purchase that doesn't expire.

When the period ends, the app reverts to the free version automatically. Your observations and notes are kept. If you need a refund, contact the app store's customer support per Apple's or Google's terms.

Many probability-based apps use a similar static approach (forest data + habitat requirements), but Tattis adds a dynamic weather layer and phenology — meaning it predicts when mushrooms appear, not just where. So there's no point heading out for chanterelles back in May.