In winter, when trees are stripped of their leaves, peculiar growth – or rather decorative works of nature – can be observed on various tree trunks. In Latvia the phenomenon is known by the name of "chaga", sometimes referred to as Inonotus obliquus – a parasitic fungus that feeds on the living tree.
Picture: chaga mushroom or Inonotus obliquus
Chaga evolves on various trees, most often on birches, less often on grey alders, and even less frequently – on aspen, rowan, and maple trees. It grows slowly, reaching about 3 kilograms per 10-20 years, by slowly sapping the tree and amassing nutrients. The tree becomes weak and sooner or later dies.
Picture: chaga mushroom on a birch tree
The scientific name for the chaga mushroom is Inonotus obliquus. It usually grows on birch trees, and for this reason it is often called the black polypore of birch-trees. In fact, it is not a polypore, but a growth caused by a parasitic fungus as the mycelium of the growth does not contain any spores. Reproduction occurs only after the tree has died. The chaga mushroom then develops an expansive fruiting body under the bark on the other side of the trunk. When it matures, the bark bursts open, revealing a hymenophore with spores, which soon become mature and ready to propagate. Their task is to enter damaged bark and cracks of the next host-tree.
Picture: one of the impressive-sized specimens – mushrooms swollen this big are a rare sight
During its life, the chaga mushroom usually grows up to 40 centimeters in diameter and 15 centimeters in width, however, some specimens are significantly larger. The shape of a chaga is usually irregular; its surface is covered with numerous cracks of various sizes and shapes, hence the bumpy appearance. Bumps of each growth are unique. If one is very diligent, he or she may probably find two similar chaga mushrooms, but no two mushrooms will look exactly the same.
Picture: chaga mushroom
The exterior part is solid, its color is black-brown, less frequently – brown or black. A cross-section of a chaga mushroom sawn off the tree reveals three layers: the external layer is solid and darkest in color; the middle layer is porous, brown, and largest in size; the internal layer, which reaches into the tree trunk – granular and fawn in color.
Picture: chaga mushroom of an unusual color
Chaga growths are quite common in Latvia, furthermore, contrary to popular belief, they can be found not only on old trees, but also on young ones. The chaga mushroom is not edible, however, it has been used in folk medicine since ancient times to improve people's general immune system, health, and to ease pain. It is also used as an anti-cancer remedy, but there is no evidence that chaga mushroom is able to treat tumors. Nevertheless, the placebo effect has a positive aspect – the patient believes in the healing attributes of chaga and therefore feels better.