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Rocky Mountain iris, western blue flag

Hartweg's iris, rainbow iris, Sierra iris

Rhizomes

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

roots fleshy.

creeping, not producing dense clumps, covered with remains of old leaves, slender to moderately thick, 0.5–0.9 cm diam.;

roots fibrous.

Stems

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

simple, solid, 0.5–3 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 deciduous, blade pale green, not pink basally, 2–4.5 dm × 0.2–0.6(–1) cm, sometimes glaucous, margins not thickened;

cauline usually 1–several, spreading, sheathing for about 1/2 length, foliaceous, blade not inflated.

Inflorescences/Inflorescence units

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.

1–2(–3)-flowered;

spathes divergent, separated by 1.5–4 cm, linear to linear-lanceolate, unequal, outer 5–11 cm × 4–7 mm, inner 5–6 cm × 2–3 mm, herbaceous, apex acute.

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 lavender, cream, or pale to deep yellow;

floral tube funnelform, 0.5–1(–1.5) cm;

sepals oblanceolate, 4–7 × 1.4–2 cm, base gradually attenuate;

petals narrowly oblanceolate, 3.5–6 × 0.5–1.1 cm, widest at about 1/2 their length, base abruptly attenuate, claw 1–2 mm wide;

ovary nearly cylindrical, 1–2 cm;

style 1.6–3 cm, crests overlapping, obtusely angled, 0.5–1.1 cm;

stigmas acutely triangular, margins entire;

pedicel 0.5–2.5 cm at anthesis, lengthening to 3.5–7.5 cm at maturity.

Capsules

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

oblong-oval, 3-angled, tapering abruptly at either end, 2–3 cm.

Seeds

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

brown, irregularly D-shaped, wrinkled.

2n

= 38.

= 40.

Iris missouriensis

Iris hartwegii

Phenology Flowering May–Jul. Flowering Jun.
Habitat Wet meadows, roadside ditches, margins of streams Yellow-pine forests on sunny or partially shaded slopes
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
CA
[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.)

Plants with pedicels 2.8–4.7 cm, and flowers light purple or bluish violet have been recognized as subsp. australis. Plants having a 3-flowered inflorescence unit, leaves about 1 cm wide, and pale yellow flowers with golden yellow veining have been called subsp. columbiana. Plants having both flowers open at the same time rather than consecutively, pedicels averaging only 1 cm, long narrow style arms and crests, and floral tubes 1.2–1.5 cm have been named subsp. pinetorum.

Iris hartwegii hybridizes with I. douglasiana, I. innominata, I. macrosiphon, I. munzii, I. tenax, and I. tenuissima. It is known from Butte County to Kern County.

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

Source FNA vol. 26, p. 388. FNA vol. 26, p. 385.
Parent taxa Iridaceae > Iris > subg. Limniris > sect. Limniris > ser. Longipetalae Iridaceae > Iris > subg. Limniris > sect. Limniris > ser. Californicae
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. 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. versicolor, I. virginica
Synonyms I. arizonica, I. longipetala var. montana, I. montana, I. pariensis, I. pelogonus, I. tolmieana I. hartwegii subsp. australis, I. hartwegii var. australis, I. hartwegii subsp. columbiana, I. hartwegii subsp. pinetorum, I. pinetorum
Name authority Nuttall: J. Acad. Nat. Sci. Philadelphia 7: 58. (1834) Baker: Gard. Chron., n. s. 6: 323. (1876)
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