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■ (SPEC) Iris prismatica Pursh

1814, botanical author Pursh

Iris prismatica Pursh ( Friedrich Traugott Pursh, 1814, Eastern United States); Section Limniris , Series Prismaticae .

'Prismatica'. (Fernald, M.L., 1947, Brackish or salt marshes along the coast from northeastern Maryland and Delaware to southern Maine and on Cape Breton); Iris prismatca var. prismatica Fern. In Contributions to the Grey Herbarium p. 134, 1947; His original description is "leaves terminating new stolons 2-5 mm. wide, shallowly or obscurely corrugated; valves of spathe pale brown, wholly or partly scario-membranaceous, the outer one rarely foliaceous; flower 5-7 cm broad, with perianth-tube about 3 mm long; blade of sepal ovate or obovate to roundish, 1.3-2 cm broad, rather abruptly contracted to the claw; faces of capsule 6-14 (av. 9.6) mm broad; seeds 3-4 mm long" (compare to var. Austrina).

See below:

FJ-I-PRISMATICA.jpgI.prismatica01.jpgIris prismatica PD.jpgIrisprismatica01.jpgprismatica.jpgprismatica01.JPGprismatica02.JPGprismatica1.JPGPrismatica Addisonia 392.jpgprismaticaalba01.JPGprismaticaalba02.JPGprismaticamaroon01.JPGprismaticapink01.JPG


Pursh.Flora Amerr. 30. 1 Sep. 1814; Macoun;
Ker in Curtis's Botanical Magazine, table 1504
"Leaves, in tbe specimens we saw, from fix to eigbt inches high, and little more than two lines in breadth ; scape dotted over with purple. We are inclined to believe it to be a mere variety of virginica, a species which we sometimes find varying with peduncles to the full as long as in the present plant; and sometimes with a stem many times shorter than the leaves, and quite simple; our figure (in No. 703) was taken from a large specimen, and in rather too early a stage.
We have however followed Mr. Pursch (by whom it was discovered and lately introduced) in considering it as specifically distinct.. Found in North-America, growing in deep iwamps in New-Jersey, near Egg-Harbour.
Our drawing was made from a specimen which bloomed in July last, at Meffrs. Lee and Kennedy's, Hammerfmith, at the same time with two varieties of virginica; which are also said to be natives of the boggy parts of North-America."- G.
Per. 1933; Hocker 1938; Bun. 1938; Starker 1938;
Barton, Flora III 85 1823
Roem. and Schult, Syst. Veg. I p.476 1817
Baker, J.L.S. XVI. 138 (1877), Hbk. Irid. 8 (1904)
Lynch, Book of the Iris, p.73 (1904)
Dykes, The Genus Iris, page 31, 1914Description.
Rootstock , a very slender rhizome, sending out long thin stolons, which appear at some distance from the old stem.
Leaves , narrowly ensiform, acuminate, 24 by 3/8 in., glaucous, finely but not prominently ribbed.
Stem , solid, slender, wiry, bearing a reduced leaf and usually a side branch, 18-24 in. high. The terminal head is 2-3-flowered and the side branch 1-flowered.
Spathe valves , acuminate, scarious, narrow, about 1 in. long.
Pedicel , 1-2 in. long, increasing eventually to 3 or 4 inches.
Ovary , trigonal, with the corners so much exaggerated as to be almost wings.
Tube , very short but comparatively broad.
Falls . The relatively long haft expands into a small ovate blade and bears at its base two small flanges not so conspicuously marked as is usually the case with I. sibirica. The haft and the base of the blade are marked with violet veins on a greenish-white ground. The rest of the blade is pale violet with deeper veins.
Standards , lanceolate, violet, with a short canaliculate haft.
Styles , arched, narrow.
Crests , divergent, quadrate, with serrated upper edge, revolute.
Stigma , a triangular tooth.
Filaments , equal in length to the anthers, pale violet or red purple.
Anthers , deep bluish-purple.
Pollen , cream.
Capsule , trigonal with sharp projecting ridges running down each angle.
Seeds , buff-coloured, smooth, pyriform, more or less compressed and tending therefore to be cubical.
This American species is quite distinct from the rest of the sibirica group but yet sufficiently closely allied with them to be included in it.
It is characterised by the peculiarly slender, wiry, solid stem, which does not grow straight but which is curiously bent and yet erect. It is also easily distinguished by the very widely creeping rhizome, which sends up the tufts of leaves at some distance apart. The capsules are most conspicuously winged ~t the angles and contain pale brown smooth-skinned cubical seeds, distinguishable from those of any other Iris.
The flower stems are freely produced and the graceful habit of the whole plant has a charm of its own. The flowers are not large but of a pleasing pale blue colour. Seedlings have so far shown no variation and cultivation presents no difficulty. It is that of the other members of the group (see page 19). It will succeed in a position where it is in the shade during part of the day.
Addisonia 12: 1, 15. March 1927, illustrated in color;
Small in Addisonia 1927 gave more information and a colored plate see following:
Native of eastern North America. Family Iridacsae Iris Family. I. Am. Sept. 30. 1814.
The great antiquity of the slender blue-flag is definitely recorded by its geographic range — which includes all three plant-provinces eastward from the highlands, viz. the Blue Ridge, the Piedmont, and the Coastal Plain. The ancestors of this flag preserved in the highland retreats during the submergences of later geologic times sent their descendents through the Piedmont clear to the coast. At the same time it held its own in the Blue Ridge, and today it may be found either in the marshes in the coastal region, or at several thousand feet altitude in the mountains.
This dainty plant is one of the most desirable of our native irises for cultivation. It forms large clumps or extensive colonies; its underground parts, especially the long rootstocks, and slender scaly stems, are firm in texture. There are no striking characters in the flowers to distinguish them from the flowers of our other blue-flags, but the fruit is characteristic: the half -ripe pod is short and broad with little body and flat wings, but as it matures the body lengthens, becomes relatively
narrow, the wings disappear, and a narrow three-angled prismatic capsule is evolved. This opens by three short valves at the summit and allows the numerous seeds to be shaken out as it bobbs about in the wind on the slender stems. The numerous seeds and the virile rootstocks are strong arguments against it having once migrated to other regions than it now occupies and then become extinct there. In the Coastal Plain the slender blue-flag grows in the turf of bogs .often about cranberry bogs , of the pine barrens . Here its flowers are elevated above the usually depressed associated vegetation. In the mountains, its ancient home, the slender blue-flag occurs in swampy places in the flat valleys which are often submerged by slow-flowing streams during flood periods. Here there is often a peculiar association of northern and southern plants— sweet-gale (Myrica Gale) and bamboo-vine (Smilax laurifolia) grow side by side. The mountain bog-asphodel (Abama montana) is associated with the pitcher-plant (Sarracenia rubra), the leather-leaf (Chamaedaphne calyculatd) , the Appalachian cherry (Prunus cuneata) , and two other blue-flags (Iris Carolina and I. versicolor) .
The specimens from which the accompanying painting was made were collected at Apple-pie Hill, Burlington County, New Jersey, only a few miles north of Egg Harbor, cited by Pursh as the locality from which the original specimens came. In latitude the species ranges from Georgia to Nova Scotia.
The slender blue-flag has a slender, widely creeping somewhat scaly rootstock. The leaves are erect, "grass-like," two or three together. The blades are very narrowly linear, mostly less than a quarter inch wide, bright green, slenderly attenuate. The flower-stalk is slender, wiry, usually one to two and a half feet tall. The flowers are usually two or three together, arising from a narrow involucre of nearly equal bracts at the top of the stem, long-pedicelled, and often one terminating one or two slender branches. The pedicel is slender, several times as long as the ovary and exceeding the bracts, inequilateral, raising the flower above the bracts. The hypanthium surrounding the ovary is three-sided and sharply three-angled, green. The perianth-tube is short, campanulate, about half as long as the ovary. The three sepals are recurved-spreading, an inch and a quarter to an inch and three quarters long, narrowly pandurate. The blade is broadly rounded, with a white background, yellow-tinged at the base and veined and flecked with blue which merges about the edges. The claw is broad, longer than the blade, magenta-striped at the base, yellowish green at the middle with a rib but no crest, whiter on the edges and with purple veins. The three petals are spatulate, about one and a half inches long, often nearly as long as the sepals, the narrow inrolled claw veined with magenta, the longer blade pale blue with deeper-colored veins. The three stamens are fully three quarters of an inch long, with a filament and anther about equal in length, the filament, and usually the anther, also magenta-tinged. The style-branches are usually less than an inch long, linear-cuneate, magenta, deeper-colored within. The style-appendages are obliquely ovate, about a quarter of an inch long, angular-toothed. The stigma is entire, sparingly erose at the tip. The capsule is narrowly prismatic-cylindric, one to two inches long, rather sharply three-angled, thin-walled, shorter than the slender pedicels, three- valved at the apex. The seeds, in one row in each capsule-cavity, are circular, or through mutual pressure sometimes half-circular, about one sixth of an inch in diameter, brown, scarcely corky, somewhat shining.-- John K. Smail.


Cubeseed Iris; Iris boltoniana Roem. & Schult.; Iris gracilis Bigelow; Iris trigonocarpa Br. & Bondie; Iris virginica A. Gray.

Chromosome counts

2n=42, Simonet 1934.


Iris prismatica cultivars;
'Alba', 'Austrina', 'Dark Maroon', 'Georgian Bay', 'Plicata', 'Polly Spout', 'Prismatica Tullahoma'; 'Rabun White'


As yet no hybrids recorded.

Distribution and Cultivation

Distribution: The distribution of the species gives clues as to its cultural requirements, although plants in cultivation can often tolerate a wider range of variables:
The species is found in the following region: Eastern USA; including Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Delaware, Alabama, Georgia, Kentucky, Maryland, North Carolina, South Carolina, Tennessee, and Virginia

Bonap's North American Plant Atlas shows the following map reproduced by permission of Kartesz, J.T., The Biota of North America Program (BONAP). 2015. Taxonomic Data Center. ( Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2015. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)]
Cultivation: Prefers moist soil, but can be grown in good garden soil, well-drained and flourishes in full sun to part shade.

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-- Main.RPries - 2009-12-03
I Attachment Action Size Date Who Comment
FJ-I-PRISMATICA.jpgjpg FJ-I-PRISMATICA.jpg manage 26 K 19 Sep 2010 - 20:29 UnknownUser Lorena Reid photo
I.prismatica01.jpgjpg I.prismatica01.jpg manage 72 K 22 Sep 2014 - 02:59 Main.TLaurin Photo scanned from the John Weiler slide collection
Iris_prismatica_PD.jpgjpg Iris_prismatica_PD.jpg manage 23 K 21 Jan 2014 - 18:26 BobPries Photo from Plant Delights Nursery
Irisprismatica01.jpgjpg Irisprismatica01.jpg manage 63 K 19 Sep 2014 - 01:13 Main.TLaurin Photo scanned from the Adele and Lewis Lawyer slide collection
Prismatica_Addisonia_392.jpgjpg Prismatica_Addisonia_392.jpg manage 36 K 12 Nov 2013 - 12:42 BobPries Biodiversity Heritage Library
prismatica.jpgjpg prismatica.jpg manage 9 K 03 Dec 2009 - 02:56 UnknownUser Plate from Dykes' The Genus Iris
prismatica01.JPGJPG prismatica01.JPG manage 116 K 21 Oct 2014 - 12:51 Main.TLaurin Photo by Joe Pye Weed's Garden
prismatica02.JPGJPG prismatica02.JPG manage 62 K 21 Oct 2014 - 13:21 Main.TLaurin Photo by Joe Pye Weed's Garden
prismatica1.JPGJPG prismatica1.JPG manage 768 K 06 Feb 2017 - 16:28 Main.TLaurin Photo scanned from the Glenn Corlew slide collection
prismaticaalba01.JPGJPG prismaticaalba01.JPG manage 63 K 21 Oct 2014 - 13:18 Main.TLaurin Photo by Joe Pye Weed's Garden
prismaticaalba02.JPGJPG prismaticaalba02.JPG manage 63 K 21 Oct 2014 - 13:29 Main.TLaurin Photo by Joe Pye Weed's Garden
prismaticamaroon01.JPGJPG prismaticamaroon01.JPG manage 63 K 21 Oct 2014 - 13:25 Main.TLaurin Photo by Joe Pye Weed's Garden
prismaticapink01.JPGJPG prismaticapink01.JPG manage 65 K 21 Oct 2014 - 13:23 Main.TLaurin Photo by Joe Pye Weed's Garden
Topic revision: r23 - 25 Mar 2022, TLaurin
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