The Yellow iris is a unique two-block high flower found exclusively in the Gladden Fields, the very swamp wherein Isildur was slain. They can be found commonly all over the swampland, regardless of sub-biome.
Like any flower, these can be grown with a random chance of appearance by using bonemeal on the soil of Gladden Fields. Like other double-high flowers, it's also possible to use bonemeal on the plant itself to get a drop.
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Black Iris •