1924, Iris Versicolor

Addisonia page 55, Plate 316, 1924

Common Blue-flag

Native of eastern North America

Family Iridaceae Iris Family

Iris versicolor L. Sp. PI. 39. 1753.

The taxonomic botanical history of iris in America starts with this species. Linnaeus based the name, indirectly, on descriptions of plants said to have come from Virginia, Maryland, and Pennsylvania, including descriptions and figures which were supposed by

Dillenius to represent two species. The name Iris versicolor, however, has now become settled upon the common blue-flag of the northeastern States and the highlands of the South. The remote ancestors of Iris versicolor in the high Appalachian Highlands evidently gave rise to various species of Iris as the descendants spread to all points of the compass. After the ice-age. Iris versicolor or its immediate relatives spread northward, eastward, and westward, but kept mainly to the higher provinces, particularly to the Piedmont, where as a species it has settled down to a very consistent aggregate. Iris versicolor and its relative I. Carolina are the only large blue-flags that have retained a geographic continuity through all the plant provinces, from the original Appalachian Highlands to the coast.

As one would suspect, in the case of a plant that is widely distributed and an inhabitant of several plant-provinces of various altitudes, there is more variation in the size and vigor of the plants of Iris versicolor, although its flowers and fruits are reasonably constant in characters. It has had vastly more experience, so to speak, than its relative Iris Carolina, and has for some reason developed a double row of seeds in each carpel. This character, which amounts to the doubling of the number of seeds, may have resulted in its maintenance in environments more rigorous and precarious than that of its southern relative.

Iris versicolor is quite flexible in regard to natural habitats, and hence tractible in cultivation; preferring a soil in which much humus has been deposited, its native haunts are swamps, marshes, meadows, stream-banks, lakes, and ponds. Different colonies and individual plants exhibit pale and deep shades of color in the flowers, and albinos are not infrequently observed in the field. The specimen from which the accompanying illustration was made was from a native colony in the New York Botanical Garden.

The common blue-flag has a very stout horizontal rootstock. The leaves are erect and usually four to six together, with linear, often narrowly linear-attenuate, glaucous blades up to one and a half feet long. The flower-stalk is stoutish, as tall as the leaves or taller, simple or with a peduncle-like branch at the middle or above it. The flower-cluster usually exceeds the leaves, terminating a green or purplish peduncle. The main bracts are much shorter than the leaves. The flowers are much exserted from the involucre. The main bracts of the involucre are not foliaceous. The pedicels are mostly one and a half to three inches long. The hypanthium, surrounding the ovary, is usually shorter than the pedicel and bluntly three-angled. The perianth-tube is funnel-form, about one fourth of an inch long. The flowers are mostly two or three together at the ends of terminal and often of axillary peduncle-like, stoutish, glaucescent branches. The three sepals are spreading, remate, one and three quarters to two and a quarter inches long; the blade is ovate, slightly longer than the claw, crestless, mainly violet or purple and indistinctly veined with darker purple; the claw is rather broad, but less than half the width of the blade, green or yellowish green, veined with dark purple, the green running into the base of the blade where it turns to white which is veined with bright purple which runs down from the upper part of the blade. The three sepals are erect, narrowly spatulate, three fifths to four fifths as long as the sepals, purple and veined with darker purple, or whitish with purple veins near the narrow base. The three stamens are one to one and a quarter inches long, the anthers slightly longer than the filaments. The three style-branches are broadly linear, nearly or quite one and a half inches long, about one third of an inch wide, lilac with whitish margins. The style-appendages are one fourth to one third of an inch long, curved inward, semi-orbicular-quadrate, rounded at the apex and undulate-angulate. The stigmas are irregularly broadly rounded, entire. The capsules are prismatic-cylindric, or in the case of short ones somewhat ellipsoid, mostly one and a half to two and a half inches long, with a slight ridge on each side and a slightly more prominent ridge on each rounded angle, obtuse or slightly beaked, the earlier ones on pedicels shorter or longer than their length, the later ones often with longer pedicels. The seeds, borne in two rows in each carpel or cavity of the capsule, are semiorbiculate or lunate, rather thin, dark brown, slightly corky, about one third of an inch in long diameter.

John K. Small.

for more information on historic Irises visit the Historic Iris Preservation Society at

-- BobPries - 2014-12-08
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Topic revision: r1 - 08 Dec 2014, BobPries
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