Iris setosa, known as the beachhead iris or bristle-pointed iris, among other common names, is a species of flowering plant in the genus Iris of the family Iridaceae. This species belongs to the subgenus Limniris and the series Tripetalae. The plant is a rhizomatous perennial found in a wide range across and below the Arctic Circle; this range includes the United States (Alaska and Maine), Canada (including British Columbia, Newfoundland, Quebec, and Yukon), Russia (including Siberia), China, Korea, and Japan. The plant has tall branching stems; mid-green leaves; and flowers that are violet, purple-blue, violet-blue, blue, or lavender (or rarely, pink or white).
Description Iris setosa is similar in form to a miniature Japanese iris, or a shorter-lived dwarf version of Iris sibirica.
The shallowly rooted, large, branching rhizomes spread with time to create large clumps. These rhizomes are grey-brown, thick, and covered with the remains of the previous season's fibrous leaves.
Iris setosa has branched stems that are variable in height, ranging from 10 cm (5 in) to 1 m (3 ft) tall. The larger plants can grow beyond the height of the leaves. The roundish stems are in diameter with 1 to 3 branches.
Iris setosa has grass-like,Fran Kelso and Frances Kelso Graham, . lanceolate (sword-shaped), medium-green leaves with a purple-tinged base. The plant's leaves can measure 30–60 cm (12–24 in) long by wide.
The plant bears 3–4 flowers per stem—for a total of between 6 and 13 on the whole plant— in groups of 3. It blooms between June and July.
The large flowers measure 5–8 cm (3–6 in) across, usually . Depending on their location, they bloom in a range of shades including violet, purple-blue, violet-blue, blue, and lavender. Very occasionally, there are pink or white forms.
Like other irises, the plant has two sets of three petals: three large sepals (outer petals), known as the "falls", and three smaller inner petals (or tepals), known as the "standards". The sepals can be deeply veined dark purple with a yellow-white center, known as the "signal". The small standards appear almost as bristles, which gives the flower a flat, three-petaled appearance.
The perianth tube (floral tube) is about long, normally dark blue-violet to red-purple with darker veins.
The plant is self-fertilizing (a hermaphrodite) and can also be pollinated by insects. The stamens are about long with purple anthers, and the ovary is about long.
After the flowers finish blooming, the seeds ripen between August and September. These seeds are contained within a green seed capsule (measuring 2.5 cm by 1.25 cm), which is loculicidal or cylindrical, and it turns pale brown when it ripens. It has six ribs along its sides.
The pale-brown to dark-red seeds, about 2–3 mm in size, have a distinct raised raphe (tissue ridge) along the length of one edge.
Biochemistry In 2012, a genetic study was performed on Iris laevigata and several closely related species; these include Iris ensata, Iris setosa, Iris halophila, Iris scariosa, Iris potaninii, Iris tenuifolia, Iris bloudowii, and Iris sanguinea. Flavonoids (a class of metabolites) have also been analysed from the flowers and leaves of the Iris japonica,ARISAWA et al., 1973 Iris pseudacorus,WILLIAMS et al., 1986 Iris gracilipes,HAYASHI et al., 1984 and Iris setosa.HAYASHI, 1984
Most irises are diploid (having two sets of chromosomes), and this characteristic can be used to identify hybrids and classify groupings. Most Iris setosa specimens have a chromosome count of 2n=38, which was determined by scientist Marc Simonet in 1934. However, specimens from the Primorskii Krai region in Russia were found to have a chromosome count of 2n=28.
Chromosomal research has found that a progenitor of Iris setosa and a progenitor of Iris virginica were the parents of Iris versicolor.
Nomenclature and taxonomy The name setosa is derived from the Latin word , meaning "bristle" or "hairy". This refers to the true petals ("standards") of the flower, which—compared to other Iris species—are nearly imperceptible.
Iris setosa has several common names, including the following:
beachhead iris, because of its tolerance for salt air or maritime conditions, as well as its growth upon rocky shorelines, especially in CanadaWilliam Cullina, . wild flag iris Alaska iris Arctic Iris or dwarf Arctic iris, because of its growth in the Arctic Circle (its scientific name was once Iris arctica) Arctic blue flag bristle-pointed iris (in the UK)
In Japan, the species is known as . In China, it is called "shan yuan wei" (山鸢尾).
The species is occasionally confused with Iris hookeri, perhaps because several synonyms of Iris hookeri are Iris setosa variants: Iris setosa var. canadensis Foster; Iris setosa f. pallidiflora Fernald; Iris setosa subsp. pygmaea C.E.Lundstr.; and Iris setosa f. zonalis Eames.
Iris setosa was first described by botanist Johann Link (based on an earlier description by botanist Peter Pallas) in in Berlin and Leipzig during 1820. The species was originally described from specimens found in eastern Siberia. A second description was then published by botanist William Rickatson Dykes (Iris 1913, p. 92) as Iris brachycuspis. In 1824, the species was also described as Iris brachycuspis by Stephan Fischer and published by John Sims in the Botanical Magazine. The names Iris brachycuspis and Iris setosa are now regarded as synonyms.
Iris setosa is a name accepted by the Royal Horticultural Society, and it gained their Award of Garden Merit (RHS AGM).
This species is one of the three Iris species in the Iris flower data set outlined by Ronald Fisher in his 1936 paper "The use of multiple measurements in taxonomic problems" as an example of linear discriminant analysis.
Distribution and habitat Range The only Iris species that is native to both Asia and North America, Iris setosa has a circumarctic distribution.
In the United States, the species ranges in Alaska from the northern Brooks Range to Southcentral Alaska and the coastal Aleutian Islands, and it is also found in Maine. In Canada, its range includes British Columbia, Newfoundland, Quebec, and the Yukon Territory.
In Russia, the range of the species includes near the lower Lena River in Siberia. In China, its range includes Manchuria and eastern Jilin. In Japan, its range includes Hokkaido and extends southward to Honshu. The species is also found in Korea.
The form of Iris setosa that grows in Canada is thought to be slightly different from the Asian form. In Canada, the species is found as far south as the shores of the Gulf of St. Lawrence and as far north as the estuary of Saint-Vallier, in Bellechasse County, Quebec.
Iris setosa is found in many of Alaska's national parks—including Glacier Bay, Kobuk Valley, Lake Clark, Wrangell–St. Elias, Katmai, and Kenai Fjords—and in Acadia National Park in Maine, though the range of the species is not limited to national parks. In Alaska, it is only found south of the Brooks Range.Tim Johnson
In Japan, the species is present in large numbers in Akkeshi, in eastern Hokkaido, Japan.
Habitat Iris setosa is normally considered a wetland plant, but it grows well in dry soil, too. The species is tolerant of many kinds of habitats, and can therefore be found in several habitats: in meadows, bogs, and swamps; beside rivers, streams, and lakes (especially on rocky shores); on beaches, dunes, and headlands; and in light woodland. The species can grow in gravelly soils and even sand. However, it is normally found at above sea level.
Conservation In 2014, two varieties of Iris setosa—hondoensis and nasuensis—were listed as critically threatened in Japan.
Cultivation Iris setosa can adapt to various conditions, except heavy clay soils that dry out in summer. The species prefers to grow in moist or wet soils; in addition, it can tolerate bog conditions, especially during the growing season, when it needs much moisture. The species dislikes soils containing lime. It prefers to grow in partial shade, because full sun risks drought conditions.
The species is also suited to sunny portions of woodland gardens or bog gardens. It is suitable for growing in front of a border. Miniature versions are also suitable for rock gardens or sinks.
As with other rhizomatous irises, the rhizome of Iris setosa should be planted with the top of the rhizome not covered by soil. If covered or planted too deep, the rhizome risks rotting.
In mild temperate areas, the plant's leaves are evergreen and can survive a winter. However, if the leaves are trimmed before winter to reduce wind interference and root disturbance, new leaves will emerge in the spring.
Some authors have suggested that irises are deer-proof. This is thought to be incorrect—it may be that leaves simply grow back after being eaten by deer.
Aphids Macrosiphum euphorbiae and Myzus ornatus can be found on the plant.R. L. Blackman, Victor F. Eastop
Hardiness
Iris setosa is one of the hardiest species of irises, but it does not grow as well in warm climates because of its need for a cold dormant period during winter. As a native plant of Alaska, it is extremely tolerant of cold temperatures down to . The plant would only be killed if it never experienced a summer.
The species is hardy to United States Department of Agriculture (USDA) Zone 3–7, 3–8, or 4–8, but it may tolerate Zone 2 and Zone 9 under perfect conditions.
Propagation Iris setosa can be propagated by seed or by division.
As with all irises, this species can be difficult to propagate from seed (in the United States). It is easier to do so by rhizome divisions, because the plant propagates naturally by rhizomes. Division is best undertaken during spring and autumn if possible, ideally in September (about 4–6 weeks after flowering). This division can be done annually, but it is better to do so every third year, or whenever the plant has spread enough that its center no longer produces any flowering stems. If the plant is only divided into thirds or quarters, the new divisions can be planted immediately; however, if it is divided into small sections to maximize propagation, these should be placed in a cold frame until the following spring, by which time they should have grown new roots.
The species is easier to grow from seed in the United Kingdom, because the seed requires a cold period (a freeze/thaw period). Seeds of the iris can be shaken from the seed capsule during mid-August. These seeds should be planted into beds or trays in a cold frame, sown into drills (furrows) 1/4 to 1/2 inch deep. If not sown immediately, the seeds should be frozen for storage. In the spring, when they are large enough to handle, the seedlings should be extracted and placed into individual pots. These can then be grown in a greenhouse or a cold frame for their first year, and then planted in their permanent locations during late spring or early summer. New plants should be planted in September. It takes at least two years to grow a plant from seed to flowering plant.
Hybrids and cultivars In the wild, Iris setosa forms hybrids with I. versicolor, the larger blue flag iris. Specimens of such hybrids have been observed on Anticosti Island, Quebec. Iris setosa also hybridizes very easily with other Iris species, including Siberian and Californian irises, and is therefore often used by breeders of iris hybrids.
Many variants are known around the world, including three in Japan, each only found in limited areas of Honshu island.
Japanese variants The hondoensis variety of Iris setosa was found in Hondo in 1930. This variety has large purple flowers and is low-branching, robust, and approximately high. The variety is assumed to be a hybrid with Iris laevigata.James Cullen, Sabina G. Knees, H. Suzanne Cubey (Editors) Var. hondoensis has chromosome numbers of 2n=54, but it may be triploid.