Firefly Bush is a light-emitting decorative plant added to Minecraft in the 1.21.5 Spring to Life drop, generating naturally in swamp biomes and on grass blocks beside water across most Overworld biomes. A Firefly Bush radiates a faint light level of 2 and releases floating firefly particles whenever the light level at its position drops to 13 or below, so Firefly Bush glows brightest at night, underground, or under a covering block. Breaking the bush drops itself instantly by hand, and applying bone meal spreads new Firefly Bush blocks to neighbouring grass, mangrove roots, or mud, making the plant fully renewable. Wandering traders also sell Firefly Bush as an alternative source.
Builders use Firefly Bush for ambient path lighting, mystical groves, and swamp-accurate dioramas, because the dim light level of 2 never melts ice or floods crops. A Firefly Bush in a composter raises the level by 30%, matching the value of most small flowers and grasses. Note that the bush is flammable and can catch fire from a flint-and-steel or spreading flame, yet the leaves will not ignite from nearby lava. Pair Firefly Bush with lily pads, moss, and pale oak logs for a fairy-tale wetland build that stays alive after dark without any redstone lamp.