In FFXIV, Bayberry is a crafting material gathered by Botanists. It was introduced as a new Legendary crafting material in Patch 6.2 after the release of Endwalker.
As indicated by the map above, it can be found in Labyrinthos starting at 4:00 a.m. and 4:00 p.m. It will then remain available for two in-game “hours” until 6:00 a.m. and 6:00 p.m. Eorzea Time, respectively.
Besides its time-limited nature, Bayberry also has a required Perception stat of 3,600. Meaning any Botanist player must have at least 3,600 Perception to even attempt gathering Bayberry. This can be achieved through a mix of gear, Materia, and temporary in-game food buffs. Particularly with the use of “overmelding.”
Bayberry will appear inside of a Level 90 “Legendary” node when it spawns. This will alert Botanists inside Labyrinthos at the time to its presence with an onscreen message and a gathering icon on the mini-map.
You can use five pieces of Bayberry, alongside two pieces of Palebloomd Kudzu Cloth, to craft Bayberry Cloth. This is a vital component in crafting several Level 90 master recipe items (i.e. high-tier Level 90 gear).
There is currently no other way to (reliably) acquire Bayberry in FFXIV. However, players can freely trade it amongst themselves and sell or buy it from the in-game Market Board.