You can find The Botanica dungeon within Tempest Keep, Netherstorm.
The coordinates are (71.4,54.8)
1. Commander Sarannis
2. High Botanist Freywinn
3. Thorngrin the Tender
/i Allergic Reaction deals high damage & has chance to spread to nearest player. Elemental Shift increases & decreases his resistance to elements. Teleports to platform & summons thorn adds.
5. Warp Splinter
/i Stomp deals damage & increases physical damage taken by 550 to players. Arcane Volley deals arcane damage to all players. Summons 6 saplings that will heal boss if they reach him, kill quickly.