Flora of the Southeastern United States
2022 Edition

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Key to Iridaceae

1 Inflorescence a spike or panicle of spikes; plants from corms; flowers slightly zygomorphic.
..2 Stem usually branched, the inflorescence appearing paniculate; tepals orange to red
..2 Stem unbranched, the inflorescence a spike; tepals any of a wide range of colors (including orange and red)
....3 Inflorescence bent at its base, the inflorescence axis more-or-less horizontal, the flowers facing upward
....3 Inflorescence erect, the flowers facing outward
1 Inflorescence an umbellate 1-sided cyme; plants from rhizomes or bulbs; flowers actinomorphic.
......4 Leaves planar; plants from rhizomes (or indistinct) or a bulb (in Iris xiphium).
........5 Style branches broad, petaloid, terminating in paired crests
........5 Style branches not broad or petaloid.
..........6 Tepals 16-35 mm long, orange or red; seeds 4-6 mm in diameter
..........6 Tepals 6-15 mm long, blue, purple, lavender, pink, magenta, white, or yellowish-white; seeds 0.6-1.3 mm in diameter
......4 Leaves plicate; plants from bulbs.
............ 7 Tepals unequal, the inner whorl < ½ as long as the outer whorl
............ 7 Tepals nearly equal in length.
............ ..8 Style recurved, with 3 flat branches that are < 2 mm long
............ ..8 Style straight, each of the 3 branches further divided into slender lobes
............ ....9 Style branches divided for ca. ½ their length; style arms arching over or between the anthers; tepals dark purple
............ ....9 Style branches divided nearly to base; style arms extending horizontally between the anthers; tepals blue, white in the center

Key to Iris

1 Plant from an ovoid bulb; [subgenus Xiphium; or genus Xiphion]
1 Plant from short to elongate rhizomes.
..2 Style branches not broad, petaloid, or crested; seeds black, shiny, in a blackberry-like cluster (the seeds exposed at maturity by dehiscence of the papery to chartaceous capsule walls); [genus Belamcanda]
..2 Style branches broad, petaloid, terminating in paired crests; seeds tan to brown, in a capsule.
....3 Sepal "signal" (see above) of multicellular hairs (the “beard”), along the midrib of the claw and the base of the blade; [subgenus Iris; or genus Iris].
......4 Aboveground stem <1 cm tall; floral tubes 6-10 cm long
......4 Aboveground stem 60-120 cm tall; floral tubes 1-2.5 cm long
........5 Spathes green (or purplish) and herbaceous, with scarious margins
........5 Spathes scarious, silvery-white
....3 Sepal "signal" consisting of contrasting color, ridges, small unicellular hairs, and/or a cockscomb-like crest.
..........6 Rhizome branches cord-like, with scale-like leaves, enlarging at the apex to produce vegetative leaves, additional branches, and flowering stems.
............ 7 Stems 30-80 cm tall; leaves 30-60 cm long, 0.2-0.7 cm wide; cordlike portions of rhizomes to 4 dm long; [of wetlands]; [section Limniris, series Prismaticae; or genus Limniris]
............ 7 Stems 2-15 cm tall; leaves 10-45 cm long, 0.3-2.5 cm wide; cordlike portions of rhizomes to 2 dm long; [of dry to mesic uplands].
............ ..8 Sepal "signal" a 3-ridged, toothed crest; leaves 10-25 mm wide, green, falcate; flowers not or only slightly fragrant; rhizomes surficial (one can "pull" them off the ground by gently tugging on the leaves); [generally of mesic and fertile soils]; [section Lophiris; or genus Lophiris]
............ ..8 Sepal "signal" merely a primarily orange color patch (not a crest); leaves 3-13 mm wide, blue-green, straight or nearly so; flowers strongly fragrant; rhizomes deeply buried (not easily "pulled"); [generally of dry and acid soils]; [section Limniris, series Vernae; or genus Gattenhofia].
............ ....9 Leaf-bearing offshoots spaced at 0.2-3 cm along the rhizome, thus forming tight to loose clumps of 2 or more leafy, above-ground shoots; rhizomes 2.5-8 mm in diameter, typically irregular, knotty, and contorted, scales not obvious; leaves 5-13 mm wide, with 15-29 veins; capsules 1.7-3.2 cm long; [in and west of the w. Piedmont and Appalachians and extending to the Gulf Coastal Plain in GA, FL, AL, and MS]
............ ....9 Leaf-bearing shoots spaced at intervals of (5-) 8-15 cm along the rhizome, thus forming colonies with well-spaced, individual, leafy above-ground shoots; rhizomes 1-2.5 mm in diameter, bearing obvious and well-spaced scales; leaves 3-8 mm wide, with 9-19 veins; capsules 1.2-1.8 cm long; [of the Coastal Plain and e. Piedmont, from e. VA to e. GA]
..........6 Rhizome branches like the primary rhizome, not as above.
............ ......10 Petals 1-2 cm long; [section Limniris; series Tripetalae; or genus Limniris]
............ ......10 Petals 2-9.5 cm long.
............ ........11 Stems hollow; [section Limniris; series Sibirica; or genus Limniris].
............ ..........12 Spathes herbaceous at flowering time; capsule 3.5-5.5 cm long
............ ..........12 Spathes scarious at flowering time; capsule 2-3.5 cm long
............ ........11 Stems solid.
............ ............ 13 Capsules 3-angled or nearly round in cross-section; [section Limniris; series Laevigatae; or genus Limniris].
............ ............ ..14 Perianth yellow
............ ............ ..14 Perianth blue-violet (rarely white).
............ ............ ....15 Flowers 8-15 cm in diameter; leaves 0.5-1.5 cm wide; [alien, cultivated, rarely escaped]
............ ............ ....15 Flowers 6-8 cm in diameter; leaves 1-4 cm wide; [native].
............ ............ ......16 "Signal" a greenish-yellow, papillate patch, surrounded by an area of heavily veined purple-on-white; [of VA northward]
............ ............ ......16 "Signal" a bright yellow, pubescent patch.
............ ............ ........17 Plants to 10 dm tall, usually with 1-2 well-developed branches; capsule 7-11 cm long
............ ............ ........17 Plants to 6 dm tall, little or not at all branched; capsule 4-7 cm long
............ ............ 13 Capsules 6-angled or ridged in cross-section; [section Limniris, series Hexagonae; or genus Phaeiris].
............ ............ ..........18 Perianth dull copper or orange-brown (or dark yellow) (fading in nature or drying in the herbarium to a bluish or purplish color); petals spreading or declining
............ ............ ..........18 Perianth blue-violet (rarely white); petals erect to spreading.
............ ............ ............ 19 Stems declining or semi-erect, sharply zigzag
............ ............ ............ 19 Stems erect, slightly if at all zigzag.
............ ............ ............ ..20 Capsules 2.5-3.5 cm long, hexagonal in cross-section, 3 sides flat, the alternating sides with 2 rounded ridges separated by a shallow groove
............ ............ ............ ..20 Capsules 6-10 cm long, slightly to strongly hexagonal in cross-section.
............ ............ ............ ....21 Capsules with 6 broad rounded lobes, indehiscent
............ ............ ............ ....21 Capsules with 6 sharp or winglike ridges, dehiscent.
............ ............ ............ ......22 Capsule ridges sharp
............ ............ ............ ......22 Capsule ridges winged