Yellow Iris (EwA Guide to Common Invasive Species in Middlesex County (MA, US) )

Yellow Iris

Iris pseudacorus

Summary ⁵

Iris pseudacorus, the yellow flag, yellow iris, or water flag, is a species of flowering plant in the family Iridaceae. It is native to Europe, western Asia and northwest Africa. Its specific epithet pseudacorus means "false acorus", referring to the similarity of its leaves to those of Acorus calamus (sweet flag), as they have a prominently veined mid-rib and sword-like shape. However, the two plants are not closely related. The flower is commonly attributed with the fleur-de-lis.

Description ⁶

This herbaceous flowering perennial plant grows to 100–150 cm (39–59 in), or a rare 2 m (6 ft 7 in) tall, with erect leaves up to 90 cm (35 in) long and 3 cm (1.2 in) broad. The flowers are bright yellow, 7–10 cm (2.8–3.9 in) across, with the typical iris form. The fruit is a dry capsule 4–7 cm (1.6–2.8 in) long, containing numerous pale brown seeds.

I. pseudacorus grows best in very wet conditions and is common in wetlands, where it tolerates submersion, low pH, and anoxic soils. The plant spreads quickly, by both rhizome and water-dispersed seed. It fills a similar niche to that of Typha and often grows with it, though usually in shallower water. The rhizomes can survive prolonged dry conditions while it is primarily an aquatic or marginal plant.

Both the petals and stem are toxic to animals and plants.^{[citation needed]}

Invasiveness ⁶

In some regions (including the USA and South Africa) where it is not native, 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.

Iris pseudacorus is reported as invasive in Connecticut, Delaware, Maryland, New Hampshire, New Jersey, North Carolina, Oregon, Tennessee, Virginia, Vermont, Washington, Wisconsin, and West Virginia.

🚧 Control Methods (EwA Content Development in Progress) ⁷

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Sources and Credits

(c) Bill MacIndewar, some rights reserved (CC BY-NC), uploaded by Bill MacIndewar, https://www.inaturalist.org/observations/120139628
(c) Daniel Onea, some rights reserved (CC BY-NC), uploaded by Daniel Onea, https://www.inaturalist.org/observations/79877573
(c) Jennifer Clifford, some rights reserved (CC BY-NC), uploaded by Jennifer Clifford, https://www.inaturalist.org/observations/47404430
(c) miguel1958, some rights reserved (CC BY-NC), uploaded by miguel1958, https://www.inaturalist.org/observations/138772598
(c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Iris_pseudacorus
Adapted by Claire O'Neill from a work by (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Iris_pseudacorus
(c) Claire O'Neill, some rights reserved (CC BY-SA)

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Yellow Iris

Summary 5

Description 6

Invasiveness 6

🚧 Control Methods (EwA Content Development in Progress) 7