Zwackhia viridis (Ach.) Poetsch & Schied.

Crustose lichen, distinguished from similar and more common Opegrapha niveoatra by usually shorter, more densely clustered hysterothecia and specific multiseptate spores with a distinct perispore. It typically grows on smooth bark of deciduous trees, particularly hornbeam, beech and sycamore, rarely on conifers. Zwackhia viridis prefers stands with humid mesoclimate, such as scree forests, beech forests and valley hornbeam forests, where it also tolerates shading. It is primarily found in lowlands and hills, but also in mountain mixed and beech forests. Locally more frequent in suitable forest stands, as evidenced by rather abundant recent findings from the Czech Republic. The species occurs scattered in central Europe.

Ascomycota → Arthoniomycetes → Arthoniales → Lecanographaceae → Zwackhia