The Dungeon Growths patch, written by Pasi Kallinen, adds code that enables plant life of various forms to grow and spread in the dungeon. It is most notably incorporated into the popular UnNetHack variant of the game.
The patch contains two major elements: herb growth and tree growth.
The patch considers certain plant-based items to be herbs. When left on an appropriate tile for a long time, these items have a chance of multiplying.
Land herbs multiply when left on the floor:
Water herbs multiply while underwater:
Trees in the dungeon can potentially seed trees to nearby squares. While this growth is slow, it can mean that unattended trees can become dense forests by the time levels are revisited in the ascension run.