Yellow flag

Iris pseudacorus

''Iris pseudacorus'' is a species in the genus ''Iris'', of the family Iridaceae. It is native to Europe, western Asia and northwest Africa. Its specific epithet, meaning "false acorus," refers to the similarity of its leaves to those of ''Acorus calamus'', as they have a prominently veined mid-rib and sword-like shape.
Yellow Flag - Iris pseudacorus *The petals look a little narrow, but I think the ID is correct.

Introduced as a garden plant from Europe. 

Habitat: Growing in a wetland Geotagged,Iris pseudacorus,Spring,United States,Yellow flag,iris

Naming

In some regions it has escaped from cultivation to establish itself as an invasive aquatic plant which can create dense, monotypic stands, outcompeting other plants in the ecosystem. Where it is invasive, it is tough to remove on a large scale. Even ploughing the rhizomes is often ineffective. It has been banned in some areas but is still widely sold in others for use in gardens.
Yellow Flag - Iris pseudacorus Introduced as a garden plant from Europe. It is considered an invasive weed in Connecticut. 

Habitat: Growing abundantly along the edge of a pond Geotagged,Iris pseudacorus,Spring,United States,Yellow flag,iris,yellow iris

Uses

The rhizome has historically been used as an herbal remedy, most often as an emetic. When applied to the skin or inhaled, the tannin-rich juices can be acrid and irritating.

This plant has been used as a form of water treatment since it has the ability to take up heavy metals through its roots.

References:

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Taxonomy
KingdomPlantae
DivisionAngiosperms
ClassMonocots
OrderAsparagales
FamilyIridaceae
GenusIris
SpeciesI. pseudacorus