Why does the Karelian birch have such an unusual pattern?

Karelian birch has a very interesting wood pattern. However, does this mean that she does not have annual rings?

It is believed that the decorative signs of this tree appeared due to a viral or genetic disease. As scientists have established, the wood pattern is inherited, but the genetic patterns of this phenomenon have not yet been determined, Techinsider reports.

As noted, it takes 5, and sometimes 10 years to understand whether the wood will have a patterned texture. Since the Karelian birch has an uneven growth of wood from the middle of the trunk, the annual rings look wavy.

This is due to the fact that mineral nutrition is disrupted, which is why the cells that give rise to new layers of wood grow unevenly. For what reason this phenomenon is observed in Karelian birches is still unclear.