From The Twilight Forest Wiki
Mushgloom plants are decorative blocks that can be found in the Dark Forest. When struck with Shears, they can be harvested for placement in other locations. They do not require tilled soil, and can be placed on any dirt block.
|1.11.2||Fixed a bug where Mushgloom could not be placed on the ground.|
|1.15.4||Cleaned up the Mushgloom texture to remove stray black pixel.|