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FNA | Family List | FNA Vol. 26 | Iridaceae

3. Sisyrinchium Linnaeus, Sp. Pl. 2: 954. 1753; Gen. Pl. ed. 5, 409. 1754.

Blue-eyed grass [Greek sys, pig, and rynchos, snout, alluding to swine grubbing the roots for food]

Anita F. Cholewa & Douglass M. Henderson†

Herbs, annual or perennial, often cespitose, rhizomatous (sometimes only obscurely, especially when cespitose) or not, sometimes with thickened, fleshy roots. Stems scapelike or branched, compressed, and 2-winged. Leaves 2–6, basal or basal and cauline, alternate, basally equitant; blade plane, ensiform, usually glabrous. Inflorescences rhipidiate, usually terminal (basal flowers occasionally produced in some montane populations), 1–11(–15)-flowered; spathes 2, opposed, green or with purplish tinge, equitant, equal or unequal, smooth to scabrous, margins hyaline, apex undifferentiated, acute to obtuse or bifid, margins of outer spathe usually connate basally. Flowers not fragrant, actinomorphic; tepals widely spreading to reflexed (S. minus and S. rosulatum with campanulate bases), ± distinct, bluish violet to light blue, white, lavender to pink, magenta, purple, or yellow, not clawed, subequal; stamens symmetrically arranged; filaments distinct, connate basally or into tube, tapering evenly to apex (basally inflated in S. rosulatum); anthers parallel, surrounding but not appressed to style branches; styles 3, erect, connate at least basally, filiform, not broad and petaloid, long, extending between stamens usually beyond anthers. Fruits capsular, ± globose, smooth to roughened by underlying seeds, apex usually rounded. Seeds many, globose to obconic or hemispheric; seed coat black, granular to rugulose. x = 8.

Species ca. 80 (37 in the flora): New World, Hawaii; 1 species in New Zealand and 1 in Great Britain probably naturalized.

Sisyrinchium is a complex polyploid taxon in which the species are not always easily distinguished. When immature, plants of branched species appear to be simple-stemmed (internodes do not elongate until just before anthesis) and those of usually simple-stemmed species occasionally are branched. White flowers may occur in otherwise blue-flowered species, and vivipary occasionally occurs. Furthermore, vegetative characteristics, while distinctive in some species, may overlap greatly in wide-ranging species. Writers of past floras sometimes were unaware of such phenotypic plasticity, or were inconsistent in their use of terminology (spathes, for instance, have variously been called leaves or valves). Some taxonomists have thought differences too subtle and chosen to lump species (e.g., S. angustifolium and S. montanum have been considered synonymous by several authors).

Flowers and spathes provide the best characters but require fresh material or extreme care during pressing. Many older herbarium collections have been misidentified due to improper collecting/pressing techniques that obscured critical characters. Additionally, variability within populations makes accurate identification based on only one individual nearly impossible. Chromosome counts can be useful in differentiating species but consistent numbers seem to be obtained only with meiotic counts. Some of the unusual counts reported in the literature were obtained with mitotic material or were from misidentified plants. A definite ploidal series seems to be evident, however, at least among the blue-flowered species. Limited breeding studies have shown that ploidal levels are strong barriers to reproduction (A. F. Cholewa and D. M. Henderson 1984; D. M. Henderson 1976). There is some indication, however, that true hybrids may exist (D. B. Ward 1959; D. S. Correll and M. C. Johnston 1970; G. Ajilvsgi 1984). Much more work, especially with molecular data and cladistic analyses, needs to be done to understand species relationships.

In eastern Texas (especially) and adjacent states, intermediates between Sisyrinchium ensigerum, S. pruinosum, S. langloisii, and perhaps S. sagittiferum can be found. These have been referred to S. texanum E. P. Bicknell (D. S. Correll and M. C. Johnston 1970), and Bicknell’s original description of that entity does mention a high degree of variability. Many of the specimens that we examined that were previously labeled S. texanum exhibit character states intermediate between those of S. langloisii and S. pruinosum or S. ensigerum. The types of S. texanum that we examined (Bray s.n., NY; Bush 32, NY; Hall 636, NY) would key to S. langloisii or S. pruinosum but exhibit several intermediate character states. Further, although K. L. Hornberger (1987, 1991) and D. S. Correll and M. C. Johnston (1970) considered S. texanum synonymous with S. sagittiferum (which they described as a branched species), E. P. Bicknell (1899, 1901) clearly indicated that the latter is unbranched, and thus it probably does not play a role in S. texanum. Much more work is needed to resolve the proper disposition of S. texanum and the true nature of this complex of southern species.

Characters critical for distinguishing species of Sisyrinchium are often found in floral material, requiring extra care in collecting and pressing. Accurate identification requires examining more than one individual in order to discount uncommon or atypical character states (generally not accounted for in this key). In branched individuals, leaves will be associated with one or more branches or peduncles that are narrower than the primary stem. Peduncles are morphologically indistinguishable from branches and are, hereafter, referred to simply as branches.


Cholewa, A. F. and D. M. Henderson. 1984. Biosystematics of Sisyrinchium section Bermudiana (Iridaceae) of the Rocky Mountains. Brittonia 36: 342–363. Goldblatt, P., P. J. Rudall, and J. E. Henrich. 1990. The genera of the Sisyrinchium alliance (Iridaceae: Iridoideae): Phylogeny and relationships. Syst. Bot. 15: 497–510. Henderson, D. M. 1972. A Biosystematic Study of the Genus Sisyrinchium (Iridaceae) in the Pacific Northwest. Ph.D. dissertation. University of Washington. Henderson, D. M. 1976. A biosystematic study of Pacific Northwestern blue-eyed grasses (Sisyrinchium, Iridaceae). Brittonia 28: 149–176. Hornberger, K. L. 1987. Systematics of the Genus Sisyrinchium (Iridaceae) in the Southeastern United States. Ph.D. dissertation. University of Arkansas. Hornberger, K. L. 1991. The blue-eyed-grasses (Sisyrinchium: Iridaceae) of Arkansas. Sida 14: 597–604. Rudall, P. J., A. Y. Kenton, and T. J. Lawrence. 1986. An anatomical and chromosomal investigation of Sisyrinchium and allied genera. Bot. Gaz. 147: 466–477. Ward, D. B. 1968. The nomenclature of Sisyrinchium bermudiana and related North America species. Taxon 17: 270–276.

1 Tepals yellow to orange; seeds usually hemispherical with depression on flattened side, or globose with or without obvious depression; filaments distinct or connate only basally.   (2)
+ Tepals purple to light blue, white, lavender, pink, or magenta, occasionally yellow; seeds globose to obconic, depression absent or occasionally slight; filaments connate ± full length (only basally in S. rosulatum).   (6)
2 (1) Stems 2–8 mm wide; capsules 6–19 mm; tepals usually 12+ mm.   (3)
+ Stems 0.5–2(–2.3) mm wide; capsules 3–9 mm; tepals usually less than 12 mm.   (4)
3 (2) Stems simple; seeds 0.7–1.5 mm, hemispherical with shallow depression.   1 Sisyrinchium californicum
+ Stems branched; seeds 1.5–2.2 mm, globose, lacking depression.   2 Sisyrinchium arizonicum
4 (2) Plants annual; tepals 2.6–5 mm; seeds 0.9–1.1 mm, with deep depression.   5 Sisyrinchium cernuum
+ Plants perennial; tepals 7.5–11 mm; seeds 1–1.7 mm, with shallow depression.   (5)
5 (4) Fruiting pedicels recurved to spreading; capsules globose or turbinate to broadly fusiform.   3 Sisyrinchium elmeri
+ Fruiting pedicels ascending to erect; capsules slightly turbinate to ± globose.   4 Sisyrinchium longipes
6 (1) Perianth campanulate basally, flaring distally; plants annual or occasionally short-lived perennial; tepals lavender, pink, magenta, yellow, or occasionally white.   (7)
+ Perianth widely flaring or reflexed from base, not campanulate; plants perennial; tepals purple to violet, blue, or white.   (8)
7 (6) Stems with 3–6 nodes; filaments connate ± full length, tapering evenly, stipitate-glandular on proximal 0.8–1.2 mm; capsule turbinate to broadly fusiform, uniformly light brown.   6 Sisyrinchium minus
+ Stems with 1–2(–3) nodes; filaments connate basally or occasionally to 1/2 length, inflated basally, stipitate-glandular on proximal 0.5–0.8 mm; capsule ± globose, bicolored, sutures and sometimes apex purplish, intrasuture surface tan.   7 Sisyrinchium rosulatum
8 (6) Rhipidia usually paired, rarely borne singly, sessile or rarely outer with branch to 7 mm; rhipidia and associated spathes closely subtended by enveloping bractlike leaf (because the 2 rhipidia are nearly enveloped by the leaf, these species can be mistaken as having a single rhipidium).   (9)
+ Rhipidia borne singly, terminating stem or branch; rhipidium and associated spathes not subtended by leaf.   (10)
9 (8) Stems 1.5–3.4 mm wide, obviously winged, not wiry.   8 Sisyrinchium albidum
+ Stems 0.5–1 mm wide, hardly or not winged, wiry.   9 Sisyrinchium capillare
10 (8) Stems branched or populations predominantly with branched individuals (see discussion).   (11)
+ Stems simple or populations predominantly with simple-stemmed individuals.   (33)
11 (10) Stems with 2–5 nodes; spathes ± equaling branches in width.   10 Sisyrinchium dichotomum
+ Stems with 1–3 nodes; spathes much wider than branches.   (12)
12 (11) Main stems usually more than 2 mm wide.   (13)
+ Main stems usually 2 mm or less wide.   (21)
13 (12) First internode equaling or shorter than longest leaf, if equaling leaves then apex of hyaline margins of inner spathe acute to acuminate.   (14)
+ First internode equaling or longer than longest leaf, if equaling leaves then hyaline margins of inner spathe broadly obtuse or acute apically.   (16)
14 (13) Stems and leaves glabrous; hyaline margins of inner spathe broadly acute to obtuse or truncate apically, sometimes projecting as lobes.   11 Sisyrinchium ensigerum
+ Stems and leaves usually scabrous, at least apically on margins; hyaline margins of inner spathe tapering to acute to acuminate apex, never projecting as lobes.   (15)
15 (14) Leaf bases persistent as fibrous tufts; outer spathe 0.5–1.8 mm longer than inner.   12 Sisyrinchium xerophyllum
+ Leaf bases not persistent or fibrous; outer spathe 2.5–5.5 mm longer than inner.   13 Sisyrinchium pruinosum
16 (13) Leaf bases persistent as fibrous tufts.   14 Sisyrinchium nashii
+ Leaf bases not persistent or fibrous.   (17)
17 (16) Hyaline margins of inner spathe 0.1–0.3 mm wide; e of the Rocky Mountains.   (18)
+ Hyaline margins of inner spathe (0.1–)0.4–1.1 mm wide; w of the Rocky Mountains.   (19)
18 (17) Capsules dark brown or black; plants usually drying dark olive green, bronze, or blackish.   15 Sisyrinchium angustifolium
+ Capsules tan to nearly white; plants drying light green to yellowish green.   16 Sisyrinchium strictum
19 (17) Hyaline margins of inner spathe usually equaling or longer than green apex; foliage strongly glaucous; tepals pale blue.   17 Sisyrinchium funereum
+ Hyaline margins of inner spathe usually shorter than green apex; foliage various but usually not strongly glaucous; tepals usually bluish violet to violet-purple.   (20)
20 (19) Outer tepals elliptic to oblanceolate; stem margins white or translucent cartilaginous; filament column usually stipitate-glandular.   18 Sisyrinchium radicatum
+ Outer tepals often broadly cuneate; stem margins same color and texture as stem body; filament column usually not stipitate-glandular.   19 Sisyrinchium bellum
21 (12) Margins of outer spathe connate basally (1.5–)2–4 mm (–5 mm in S. langloisii).   (22)
+ Margins of outer spathe connate basally 3.5–9 mm.   (26)
22 (21) Outer spathe 2.5–5.5 mm longer than inner; spathes usually scabrous.   13 Sisyrinchium pruinosum
+ Outer spathe shorter or no more than 2.7 mm longer than inner; spathe usually glabrous.   (23)
23 (22) Leaf bases persistent as thick, fibrous tufts.   20 Sisyrinchium fuscatum
+ Leaf bases not persistent as fibrous tufts.   (24)
24 (23) Ovary and capsule black, contrasting with much lighter foliage; hyaline margins of inner spathe broadly rounded or truncate apically.   21 Sisyrinchium atlanticum
+ Ovary and capsule not contrasting with foliage; hyaline margins of inner spathe usually acuminate to acute or sometimes obtuse apically.   22 Sisyrinchium langloisii
26 (21) Ovaries and capsules black, contrasting with much lighter foliage.   21 Sisyrinchium atlanticum
+ Ovaries and capsules not contrasting with foliage.   (27)
27 (26) Hyaline margins of inner spathe broadly rounded or truncate apically.   (28)
+ Hyaline margins of inner spathe usually acute or acuminate apically.   (30)
28 (27) Hyaline margins of inner spathe usually equaling or longer than green apex; foliage strongly glaucous; tepals pale blue.   17 Sisyrinchium funereum
+ Hyaline margins of inner spathe usually shorter than green apex; foliage various, not strongly glaucous; tepals bluish violet to violet-purple.   (29)
29 (28) Outer tepals elliptic to oblanceolate; stem margins white or translucent-cartilaginous; filament column usually stipitate-glandular.   18 Sisyrinchium radicatum
+ Outer tepals often broadly cuneate; stem margins similar to stem body; filament column usually not stipitate-glandular.   19 Sisyrinchium bellum
30 (27) First internode equaling or shorter than leaves.   (31)
+ First internode longer than leaves.   (32)
31 (30) Plants drying brownish olive to bronze; rhizomes obvious.   23 Sisyrinchium miamiense
+ Plants drying yellowish green to olive, occasionally bronze; rhizomes scarcely discernable.   24 Sisyrinchium biforme
32 (30) Capsules 4–7.5+; sw United States.   25 Sisyrinchium demissum
+ Capsules 3.5–4.9 mm; Great Lakes region.   16 Sisyrinchium strictum
33 (10) Margins of outer spathe distinct basally or rarely connate to 1 mm, and then stems greater than 1.5 mm wide, glabrous or scabrous.   26 Sisyrinchium campestre
+ Margins of outer spathe obviously connate basally 1 mm or more (rarely connate less than 1 mm and then spathes tinged strongly purple), usually glabrous or rarely slightly scabrous.   (34)
34 (33) Leaf bases persisting in fibrous tufts.   35 Sisyrinchium sagittiferum
+ Leaf bases not persisting in fibrous tufts.   (35)
35 (34) Rhizomes obvious and elongate; tepals purple to dark reddish purple or very rarely bluish violet, base purple.   30 Sisyrinchium hitchcockii
+ Rhizomes scarcely discernable; tepals bluish violet, occasionally purple or purplish blue, to light blue or white, base yellow.   (36)
36 (35) Spathes subequal, or outer up to 4.5 mm longer than inner.   (37)
+ Spathes distinctly unequal, outer at least 6 mm longer than inner.   (38)
37 (36) Capsules 2.2–4 mm; hyaline margins of inner spathe broadly rounded to truncate apically, often extending as 2 lobes beyond green apex; w United States.   31 Sisyrinchium halophilum
+ Capsules 5–7 mm; hyaline margins of inner spathe acute to acuminate or occasionally lobed and slightly exceeding green apex; s United States and n Mexico.   24 Sisyrinchium biforme
38 (36) Tepals pale blue; outer tepals usually rounded apically to slightly emarginate.   (39)
+ Tepals blue-violet to purplish blue, occasionally purple; outer tepals emarginate, truncate or occasionally rounded apically.   (42)
39 (38) Outer tepals greater than 10 mm; Columbia River Gorge.   33 Sisyrinchium sarmentosum
+ Outer tepals 10 mm or less; elsewhere.   (40)
40 (39) Outer spathes usually connate more than 2.6 mm; outer tepals slightly emarginate to rounded apically; Colorado, Wyoming.   28 Sisyrinchium pallidum
+ Outer spathes connate less than 2.6 mm; outer tepals rounded apically, never emarginate; elsewhere.   (41)
41 (40) Capsules dark brown to black; Greenland.   36 Sisyrinchium groenlandicum
+ Capsules beige to light brown; w Canada, Washington.   37 Sisyrinchium septentrionale
42 (38) Stems with very narrow or scarcely discernable wings, almost wiry, 0.9–2 mm wide.   29 Sisyrinchium mucronatum
+ Stems obviously winged, 1–3.7 mm wide.   (43)
43 (42) Capsules 6.2–8.1 mm; outer tepals usually rounded to slightly truncate apically.   32 Sisyrinchium littorale
+ Capsules 3–6.8 mm; outer tepals usually emarginate or truncate apically (rarely rounded and capsules shorter than 6 mm).   (44)
44 (43) Outer spathes usually at least (12–)16 mm longer than inner; stems usually (1.5–)2–3.7 mm wide; keel of inner spathe ± gibbous basally; seed coat rugulose.   27 Sisyrinchium montanum
+ Outer spathes no more than 16 mm longer than inner; stems 1–2.5 mm wide; keel of inner spathe not gibbous; seed coat usually granular.   34 Sisyrinchium idahoense

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