Iris pseudacorus, also known as Yellow Iris or Yellow Flag, is a beautiful herbaceous perennial that is native to Europe, western Asia and northwest Africa. Its leaves have a sword-like shape and a prominently veined mid-rib, similar to those of Acorus calamus, which earns it the specific epithet "false acorus". This plant produces bright yellow flowers, with a typical iris form, and a dry capsule fruit containing numerous pale brown seeds. Iris pseudacorus grows best in wet conditions and is often found in wetlands, where it tolerates submersion, low pH, and anoxic soils. It spreads quickly, through both rhizome and water-dispersed seed, making it a great choice for bog gardens. Its ability to take up heavy metals through its roots makes it useful for water treatment and as an indicator plant in biology experiments. However, it can also become an invasive species in non-native regions, where it out-competes other plants and can be difficult to remove. Despite its toxic qualities, the rhizome has been historically used for herbal remedies and ink-making. This stunning plant has gained the Royal Horticultural Society's Award of Garden Merit and is a must-have for any water garden enthusiast.