Old man's beard can refer to several types of plants. Leaves on these plants usually hang down and often resemble an old man's beard. Several species of lichen have this nickname. Some trees, shrubs, and climbing plants also have this nickname.
In the genus Usnea, there are a variety of plant species that have the nickname old man's beard. Some of these species are also colloquially referred to as beard lichen. A lichen is a type of plant that is basically a combination of fungus and algae. It can often be found growing on rocks and trees.
These plants resemble an old man's beard because they have hanging or draping foliage that is either green or gray. These types of lichen can be found growing in Europe, Asia, and North and South America. Uses of old man's beard are primarily medical. Many species have antiviral and antibacterial properties, for example. They are often used as herbal remedies for humans as well as wildlife.
Spanish moss, or Tillanda useoides, is another plant that has the nickname of old man's beard. This flowering plant looks very similar to some of the lichen mentioned above, but it is typically found draped in trees in the southeastern United States. In the past, it has been used for insulation, mulch, and mattress stuffing. It was even used to stuff some of the first automobile seats. Today, it can be found in craft stores, and many people use it for its decorative qualities.
Clematis aristata is a climbing shrub that is also sometimes referred to as old man's beard. It is native to Australian forests. The star-shaped flowers on this plant are usually white or off white, and they can grow to be as large as 3 inches (7.6 centimeters). Many gardeners enjoy growing old man's beard of this sort because it does well in shady areas. If it is not maintained properly, however, it can smother other plants.
New Zealand has a plant nicknamed old man's beard as well, which is known scientifically as Clematis vitalba. The fruits of this plant have flowing white tufts that can resemble a white beard when there are several together. Since it can propagate and grow rapidly, Clematis vitalba is now considered to be an invasive species.