|This article is about an older version of DF.|
Mud is created by flooding an area with water. Creating mud is required for growing subterranean crops. The only way to obtain mud for farming is via irrigation, whether manual (using floodgates) or automatic (from seasonal floods).
Once the cave river has been discovered, underground rough muddy tiles will spontaneously grow tower-cap trees and shrubs. Like trees and shrubs that grow outdoors, these can be harvested and will yield wood and subterranean crops. Cutting down subterranean trees will cause the floor to turn into "mud/dirt" which can no longer be smoothed but which will still support plant growth. Unlike in later versions, smoothed floors will not support plant life, even when muddy.
All subterranean mud will slowly dry up during winter.