Official Wiki for the game https://pzwiki.net/wiki/Foraging
Appear in groups of 2-8. As foraging level rises, more varieties can appear and berries are less likely to be poisonous. Character can identify poisonous berries by starting with the herbalist trait, reading the herbalist magazine, or reaching level 7 in the cooking skill. Blackberry, Blueberry, Winter berry and Beautyberry are never poisonous (). Holly berries will always be poisonous ( ).
Mushrooms
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Appear in groups of 1-4. Character can identify poisonous mushrooms by starting with the herbalist trait, reading the herbalist magazine, or reaching level 7 in the cooking skill. Mushrooms are significantly more likely to be poisonous than berries, and when they are poisonous they can be up to 5 times as poisonous as berries. No mushroom appearances are always safe or always poisonous. Can be used in stew, pie, soup, sandwich, salad, roasted vegetables.