Seeds of Stinking Iris, Iris foetidissima. December 2021.

Flowers are a bit scarce at the moment, though seasonal favourites Snowdrops and Winter Aconites are beginning to make an appearance and Winter Heliotrope has been wowing us with its scent for the past month.

Stinking Iris, Iris foetidissima, is a perennial plant with evergreen foliage. It flowers in late spring and summer (peaking in June and July, though I have seen it flowering in mid May in a sheltered spot on the Isle of Wight). Its flowers are subtly pretty (see the Wildflower Finder website) and attractive to bees but it is the brightly coloured seeds that are the highlight. These last throughout the winter and can be seen at the moment, providing a welcome splash of colour (bright orange or scarlet).

Iris foetidissima is a native of Great Britain, where it is found in hedge banks and in woods, as well as on sheltered scrubby sea-cliffs, with a preference for calcareous soils. It is considered to be an alien in Ireland. Further afield it is native to mainland France, Italy, Portugal and Spain, Morocco, Algeria and Tunisia, the Azores, Balearic islands, Corsica, Sardinia and Sicily. It has been introduced to California, the Canary Islands, Madeira, New Zealand (North Island), Switzerland, Tasmania, Turkey, the former Yugoslavia and possibly Belgium (note 1). The plant can spread vegetatively and by seed. In Britain it is a frequent a garden escape.

There is a lot of Stinking Iris in woodland sloping steeply down to the River Waveney, near Bungay, and this is where I took the photograph above.

Stinking Iris is highly tolerant of drought and shade and will grow beneath trees and even in the darkest dingiest corners. This makes it a good garden plant for difficult places and The Royal Horticultural Society (RHS) have given it an Award of Garden Merit (AGM). Alys Fowler suggests it for “jollying up the base of a leylandii hedge that you can’t get rid of, or for a dark, basement courtyard that only sees a sliver of sunlight“. The BBC Gardeners’ World website has some planting suggestions: “It works well with with other shade lovers such as Euphorbia amygdaloides var. robbiae, and under deciduous trees alongside dwarf spring-flowering bulbs.” It will grow well in sunshine and semi-shade too. Plants are easy to propagate by division and can be grown from seed (sown in late autumn).

The seeds are attractive to birds, especially Blackbirds, which eat them late in the winter. But don’t be tempted to try them. The whole plant – like other irises – is poisonous to humans and contains the toxic isoflavone iridin. Eating small quantities of the plant can cause “extreme discomfort” and symptoms of iridin poisoning in humans include vomiting and bloody diarrhoea and there are records of poisoning in pigs, which died when eating the exposed rhizomes, and in cattle, where some calves died after eating irises in a garden border (note 2).

“Foetidissima” refers to the plant’s unpleasant smell.

If you bruise or tear a Stinking Iris leaf it has a strange smell, described as “roast beef, foetid, or of sweetly acrid meat which is a bit ‘high’” and “rotten raw beef“. I can detect this beefiness. I wouldn’t exactly describe it as ‘Stinking” but it isn’t delightful either, just rather odd. Be a bit careful when handling the plant – the RHS recommends that you “wear gloves and wash hands after handling” and Cooper & Johnson warn that the sap can irritate the skin and even cause blistering (note 2).

Stinking Iris is a member of the Iridaceae (Iris family). It is one of two native species of Iris in the British Isles. The other is the Yellow Flag, Iris pseudacorus, which is better known for its bright yellow flowers. In the Western Isles of Scotland it is a favourite haunt of Corncrakes.

Other names for Iris foetidissima include Scarlet-berry Iris, Gladdon, Gladwin Iris, Roast-beef Plant, and Stinking Gladwin. “Gladdon” and “gladwin” refer to the sword-like leaves (from the Latin ‘gladius‘, note 3).

There are a few cultivars of Iris foetidissima that are worth looking out for. Alys Fowler mentions a golden-seeded variant which sounds lovely (‘Golden Seeded’ or ‘Golden Gobbet’) and there is also ‘FructuAlbo’, whose seeds are “polished white ones that sit inside the furry interior of the seed head like brilliant pearls“. Unusual leaf forms include striped (‘Variegata’) and yellow (‘Paul’s Gold’) . There is also a dwarf form.

Stinking Iris flowers are normally a mix of dull shades of mauve, blue, yellow and white.

Iris foetidissima – typical form. Topcroft churchyard, Norfolk.

Alys Fowler mentions a form with yellow flowers, ‘Citrina’. I think this is what I saw on the Isle of Wight in May 2019 and, more recently, at New Buckenham church in Norfolk.

Stinking Iris, Iris foetidissima – form ‘Citrina’, I think. New Buckenham churchyard, Norfolk.

Notes

Note 1 – Stinking Iris was first recorded in Belgium as recently as 2008. The plant is thought to have escaped from cultivation, but the Manual of the Alien Plants of Belgium website says that “a natural range extension [from northern France], cannot be ruled out”.

Note 2 – M. R. Cooper and A. W. Johnson (1988): “Poisonous Plants & Fungi – An illustrated guide”, HMSO, London.

The chemical that causes blistering is Irisquinone. It closely related to Primin, the substance that causes contact dermatitis in some species of Primula.

Note 3 – As in ‘gladiator‘. Another plant in the Iris family (Iridaceae) is Gladiolus, which means “little sword”, again from the shape of the leaves.