Cetraria islandica
Icelandic lichen: Lichen valued in traditional medicine for its antitussive and expectorant properties.
Icelandic lichen is extremely hardy, tolerating temperatures down to -25 °C, but requires very specific conditions: place it in a spot with direct sunlight for at least 3-4 hours a day and an acidic, nutrient-poor, well-drained substrate (such as peat or rock). Water very sparingly, allowing it to dry out completely between waterings, as it tolerates drought far better than excess moisture. If grown indoors, ensure good ventilation and direct light, avoiding warm and enclosed environments. Its difficulty level is high because it mimics a very specific ecosystem; focus on reproducing its natural mountain or tundra conditions.