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Rocky Mountain iris, western blue flag

blue flag, blue iris, harlequin blueflag, iris versicolore

Rhizomes

freely branching, producing large colonies, stout, 2–3 cm diam., clothed with dark remnants of old leaves;

roots fleshy.

pale pinkish white, freely branching, forming large clumps, 1–2.5 cm diam., clothed with remnants of old leaves;

roots fleshy.

Stems

simple or 1–2-branched, solid, 2.5–6 dm.

1–2-branched, solid, 2–6 dm.

Leaves

basal with blade light green, often white basally, not prominently veined, linear, 4.5–6 dm × 0.3–1.2 cm, glaucous, apex acute;

cauline 2–3, often shed with spent stem, similar to basal leaves, distal may subtend branch.

basal with blade green to grayish green, often purplish basally, centrally thickened in mature leaves, prominently veined, narrowly ensiform, 1–8 dm × 1–3 cm;

cauline 1–2, blade linear-lanceolate, seldom equaling stem.

Inflorescences

with terminal and lateral units (when present) (1–)2–3-flowered;

spathes subopposite to distant, to as much as 3–7.5 cm apart, lanceolate or ovate, keeled, outer usually shorter, 3.5–4 cm, inner 5.5–7 cm, scarious with herbaceous areas basally and along keel, apex acuminate.

compact, units 2–4-flowered;

spathes never foliaceous, 3–6 cm, unequal, outer shorter than inner, thickly chartaceous to scarious, margins shiny, darker in color.

Flowers

perianth blue to lavender to white, veined deeper violet;

floral tube green with purple veins in line with midrib of petals, funnelform, constricted above ovary, 0.5–1.2 cm;

sepals deeply veined lilac-purple, with yellow-white signal at base of limb, claw yellowish white, veined and dotted with purple, obovate, 3.7–7 × 1.2–3.2 cm;

petals slightly divergent, oblanceolate to spatulate, 3.6–7 × 0.5–1.2 cm, base gradually attenuate, apex acuminate or rarely emarginate;

ovary trigonal with 6 shallow ridges, 1–2 cm;

style 2.4–4 cm, crests quadrate, 0.7–1.4 cm, margins irregularly toothed;

stigmas 2-lobed, margins entire;

pedicel slender, 1–6 cm at anthesis, increasing to 7.5–8 cm at maturity.

perianth violet-blue to rarely white;

floral tube funnelform, constricted above ovary, 1–1.2 cm;

sepals ovate to reniform, 4–7.2 × 1.8–4 cm, base abruptly attenuate, signal a pubescent, greenish or greenish yellow patch surrounded by heavily veined purple on white at base of blade;

petals lanceolate to oblong-lanceolate, 2–5 × 0.5–2 cm, much shorter than sepals, firm, apex rarely emarginate;

ovary rounded-triangular in cross section, somewhat inflated, 0.8–2 cm;

style 3–3.5 cm, base not auriculate, margins entire or toothed, crests reflexed, 0.7–1.5 cm;

stigmas unlobed, triangular or rounded-triangular, margins entire;

pedicel 2–8 cm, frequently exceeding spathe.

Capsules

almost circular in cross section, with 6 obvious, equidistant ridges, 4–5 × 1.5 cm.

often persistent over winter, ovoid to oblong-ellipsoid, conspicuously beaked, obtusely triangular in cross section, 1.5–6 cm, tardily dehiscent.

Seeds

light brown, nearly globular to pyriform, 4–4.5 mm, wrinkled.

dark brown, D-shaped, 5–8 mm, shiny, thin, hard, regularly pebbled, not corky.

2n

= 38.

= 108.

Iris missouriensis

Iris versicolor

Phenology Flowering May–Jul. Flowering May–Jul.
Habitat Wet meadows, roadside ditches, margins of streams Marshy places, along roadsides, shores, and along mountains
Elevation 10–3000 m (0–9800 ft)
Distribution
from FNA
AZ; CA; CO; ID; MT; NE; NM; NV; OR; SD; UT; WA; WY; AB; BC; n Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
CT; MA; MD; ME; MI; MN; NH; NJ; NY; OH; PA; RI; VA; VT; WI; MB; NB; NL; NS; ON; PE; QC
[WildflowerSearch map]
[BONAP county map]
Discussion

The ecological range of Iris missouriensis is probably more varied than that of any other North American species of the genus, extending from almost sea level in southern California to 3000 m in Montana and Wyoming. There is correspondingly wide variation in a number of characters, which has caused much confusion as to taxonomic circumscription. Homer Metcalf (pers. comm.) made a detailed study of this species. The basic requirement for its success seems to be an extremely wet area before flowering and then almost desertlike conditions for the rest of the summer.

In large populations, sometimes covering hundreds of acres, Iris missouriensis may be found with either simple or branched stems, leaves from 4 mm to more than 1 cm wide, shorter than the stem or longer, only one flower to as many as three on a stem, and colors from deep blue to almost pure white. A single plant found on the Pariah Plateau in Kane County, Utah, with leaves only 3–4 mm wide and a single flower stem only 4 cm long, which meant that the flower was at almost ground level, was named Iris pariensis. No other such specimen has been located, and this entity must be considered as just an aberrant form that was due to the desertlike conditions in which it was growing.

Iris missouriensis is known to hybridize with I. longipetala.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

E. Anderson (1936) showed rather conclusively that Iris versicolor arose as an amphidiploid between I. virginica (n = 35) and I. hookeri (I. setosa var. canadensis) (n = 19). Back-cross hybrids have been produced both ways: I. virginica × I. versicolor producing Iris ×robusta E. S. Anderson, and I. versicolor × I. hookeri producing I. ×sancti-cyri J. Rousseau.

Iris versicolor is becoming a weed in New Brunswick, Prince Edward Island, and Nova Scotia. Livestock will not eat iris foliage, but feed voraciously on the competition, thus giving the irises plenty of room to expand.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 26, p. 388. FNA vol. 26, p. 390.
Parent taxa Iridaceae > Iris > subg. Limniris > sect. Limniris > ser. Longipetalae Iridaceae > Iris > subg. Limniris > sect. Limniris > ser. Laevigatae
Sibling taxa
I. bracteata, I. brevicaulis, I. chrysophylla, I. cristata, I. douglasiana, I. fernaldii, I. fulva, I. germanica, I. giganticaerulea, I. hartwegii, I. hexagona, I. hookeri, I. innominata, I. lacustris, I. longipetala, I. macrosiphon, I. munzii, I. orientalis, I. pallida, I. prismatica, I. pseudacorus, I. pumila, I. purdyi, I. savannarum, I. setosa, I. sibirica, I. tenax, I. tenuis, I. tenuissima, I. tridentata, I. verna, I. versicolor, I. virginica
I. bracteata, I. brevicaulis, I. chrysophylla, I. cristata, I. douglasiana, I. fernaldii, I. fulva, I. germanica, I. giganticaerulea, I. hartwegii, I. hexagona, I. hookeri, I. innominata, I. lacustris, I. longipetala, I. macrosiphon, I. missouriensis, I. munzii, I. orientalis, I. pallida, I. prismatica, I. pseudacorus, I. pumila, I. purdyi, I. savannarum, I. setosa, I. sibirica, I. tenax, I. tenuis, I. tenuissima, I. tridentata, I. verna, I. virginica
Synonyms I. arizonica, I. longipetala var. montana, I. montana, I. pariensis, I. pelogonus, I. tolmieana
Name authority Nuttall: J. Acad. Nat. Sci. Philadelphia 7: 58. (1834) Linnaeus: Sp. Pl. 1: 39. (1753)
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