They were implemented with R40 on Mach 29th 2017 and can be placed as decorative wooden building blocks.
Birchlike Ashenwood trees that can be found in Woodlands, Forests and Valleys between Mountains, more rarely and in rather bush-like small shapes in Grasslands, Savannahs or on top of rock formations in Canyons. Ashenwood trees can also be grown from Saplings that are occasional additional harvests when collecting Ashenwood or Ashenwood Leaves. No Power Cells are required to pick up Ashenwood Logs.
Currently (as of March 2017), Ashenwood Logs cannot be put in a Processor as a raw material for Wood Slabs nor Wood Rods unlike other Logs, and Ashenwood Logs can also not be used as a Fuel for the Forge.
Ashenwood Logs cannot be corrupted as of R40, and for now they even seem to be fire-proof as they can be placed into liquid Lava without igniting.