Wiltshire and Swindon Biological Records Centre

Yellow iris - Iris pseudacorus

Yellow Iris flower, WWT/ David Hall


One of only two native British irises, the bright yellow flowers of this plant flutter in the wind and resemble flags which give the plant its other common name of Yellow Flag. This common and widespread rhizomatous herb can be found throughout the county in wet meadows, wet woodlands, lakes, ponds, canals and rivers. Although it grows best in wet conditions it can survive prolonged dry conditions.


It is a perennial herb that grows between 1-1.5m tall and when it is in flower, from May to July, it can be easily identified. The yellow flowers are 7-10cm across and can vary in colour from a pale yellow to orange-yellow; each plant may bear up to 12 flowers. The leaves are erect and sword-like with a bluish tinge and a prominent midrib; they can grow up to 90cm long and 3cm across. Yellow Iris spreads quickly through both seed dispersal and vegetatively through the spread of rhizomes (modified underground stems which store food and which bear both roots and buds).


Yellow Iris used to be more widespread in marshes, fens and wet meadows and loss of many of these habitats through drainage in the past century means that is now more typically associated with standing and running water. However, it remains a common and familiar species in Wiltshire, and is not considered to be threatened. In fact it is often introduced to newly-created ponds and lakes as a desirable marginal plant.


Being generally protected by the Wildlife & Countryside Act 1981 it is an offence to uproot Yellow Iris without a landowner’s permission.