In October, the protected species of month - tree lungworth - can be well seen on the deciduous tree trunks in natural forests, parks, alleys and wooded pastures.

When the splendor of autumn leaves has disappeared, multicolored lichens stand out in forests and parks. Tree lungwort Lobaria pulmonaria catches the eye immediately: the leaf-like thallus with ridged lobes is much larger than other lichens. In dry weather, the surface of the lichen thallus is greyish brown, while in moisture it often turns bright green. The lichen also acquired its common name to the leaf structure, which resembles the alveolar pattern of the lungs. Tree lungwort was once used in folk medicine.

Tree lungwort is found on deciduous trees: maples, lindens, aspens, oaks, ashes, etc. in perennial forests, as well as in parks, alleys and wooded pastures. Lichens are threatened by habitat loss, they are also sensitive to air pollution.

In Latvia, the common lichen is relatively rare throughout the territory. The species is found worldwide in Europe, North America, Asia and Africa.