Gardening Magazine

Plant of the Week: Iris Pseudacorus

By Davis Landscape Architecture @DavisLandArch

Position: Flourishes in full sun to partial shade.

Soil: Moist to wet.

Flowering period: Early to mid summer.

Eventual Height: 1.5m

Eventual Spread: Indefinite

Hardiness: USDA Zone 4a-9a

Family: Iridaceae

Iris pseudacorus is a deciduous, rhizomatous perennial with an upright habit. It is primarily a aquatic plant, although the rhizomes of this plant can survive prolonged periods of dry soil conditions. It is a beardless leviagatae Iris and its foliage is ribbed, grey-green and up to 90cm long. In early to mid summer each branched stem bears 4-12 flowers that have petals with yellow, brown or violet markings and a darker yellow zone on each fall. Following the flower 4-7cm long green seed pods are formed which eventually produce pale brown seeds. The plant is spread by both rhizomes and water dispersed seeds.

Historically I. pseudacorus or Yellow Flag has been used as a herbal remedy where the rhizomatous roots were used to induce vomiting. This plant now use an important component of water treatment systems as it has the ability to absorb heavy metals through its roots. It is native to Europe, including the UK and north west Africa.

Iris is Greek meaning ‘rainbow’, probably in reference to the many colours of their flowers, with pseudacorus being derived from the Latin meaning “false acorus,” referring to the similarity of its leaves to those of Acorus calamus,

Iris pseudacorus (21/05/2011, London)

Iris pseudacorus (21/05/2011, London)

This plant may be usefull to the landscape architect in lakeside locations or in any waterlogged scheme, especially if native plants are to be preferred. This plant can also be used effectively as part of water purification system.

This plant will prefer an acid pH, in loam or clay based soil in a sheltered or exposed location facing any aspect and will also prefer waterlogged conditions.

Ecologically this plant will cater to pollinating insects such as bees.

The Royal Horticultural Society have given it their prestigious Award of Garden Merit.

Maintenance: Requires little to no care, dying foliage may be removed in autumn and flowering stems may be cut back at the end of the flowering season. As this plant spreads readily, periodic removal may be necessary to keep stands in check.

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