Harjakkeet

Harjakkeet, also known as "beard lichen," is a common name for several species of lichen belonging to the genus Usnea. These lichens are characterized by their long, pendulous, and hair-like thalli, which often hang from trees, giving them a "bearded" appearance. The thalli can range in color from pale green to greyish-green or even yellowish. They are composed of a fungal and algal symbiosis, where the fungus provides structure and absorbs minerals, while the alga performs photosynthesis.

Usnea species are found worldwide, particularly in temperate and boreal forests, and are often considered indicators of air quality. Their sensitivity to pollution means that their presence or absence can signal the health of an environment. They typically grow on the bark of trees, but can also be found on rocks or even the ground in some instances. Their growth rate is generally slow.

Historically, some Usnea species have been used in traditional medicine, particularly for their perceived antibacterial and anti-inflammatory properties. Various preparations were made for wound healing and other ailments. In some cultures, they have also been used as dyes. Modern scientific research continues to investigate the bioactive compounds found within these lichens. The ecological role of harjakkeet includes providing habitat and food sources for some invertebrates.