Siberian Iris Taxonomy

 More general iris taxonomy information is available here and in Brian Mathew's book. 
Family Iridiceae

Genus Iris

Subgenus Limniris (the beardless irises)
        
Section Limniris
          
Subsection Apogon

Series Sibiricae (SIB)
     Prefer damp conditions in mountain meadows or light woodland
     Stout rhizomes, generally hollow-stemmed, deciduous
     Three-cornered capsules, D-shaped seeds

     Subseries Sibiricae-28 chromosomes- "robust" Siberians
        Native to central Europe and eastern Asia
        Easily grown in much of the US and southern Canada.  Most
        garden plants are hybrids of I. siberica and I. sanguinea.
        Seed capsules are hard with blunt tops
        Short spathes, small flanges

        I. siberica    -- medium-narrow leaves 4mm 
                          6cm. flowers high above foliage
                          found N. Italy to Lake Baikal
        I. sanguinea   -- medium leaves 5-12mm
                          stalks shorter, unbranched
                          flowers 6-8cm., found in east Asia
        I. typhifolia  -- narrow leaves 2-3mm, found in China

     Subseries Chrysographes-40 chromosomes- "gracile" Siberians
        Native to southwestern China
        Seed capsules are delicate with spiked tops
        Long spathes, large flanges
        Can be grown in moist areas with winter protection.

        I. bulleyana      -- questionable as a species
        I. chrysographes  -- deep velvety rose/purple/black
        I. clarkei        -- wide leaves, solid stems!
        I. delavayi       -- five feet tall
        I. dykesii        -- questionable as a species
        I. forestii       -- yellow, tall flowers
        I. phragmitetorum -- extinct?
        I. wilsonii       -- yellow, wide flowers

Tetraploid Siberians

 Some Siberian irises have twice the normal number of chromosomes, most often brought about by treatment with colchicine, a technique pioneered by McEwen in 1962, and used extensively by other breeders such as Robert Hollingworth. Natural tetraploid Siberians are rare.

Characteristic of these plants are large flaring flowers of rich color, stout stalks, and wide leaves that often curve laterally. A good example of such a plant is the popular Jewelled Crown. Tetraploids are especially popular as cut flowers, while devotees of diploids consider their graceful plant form especially attractive.

References

The Iris, by Brian Mathew, Batsford, 1989, 256 pages, 38 colour photos, 32 b/w photos, 16 illustrations, ISBN 0-7134-6039-3, is a serious guide to the genus, with descriptions, classifications, and habitat information. about $33

The Siberian Iris, by Currier McEwen, 1996, 206 pages, 37 color plates, ISBN 0-88192-329-X, is a general guide to all aspects of the Siberian irises--history, classification, culture, evaluation, and hybridizing. about $40.

Repeat Bloom in Siberians

 The tendency of some Siberian irises to extend their bloom season, sometimes as an apparently continuous long season, other times in two distinct blooming spurts, is called "repeat bloom" to distinguish it from the habit of bearded irises with clearly separated bloom seasons, called "rebloom." It tends to occur on divisions at least two years old. Extended comments about this tendency and its mechanism appear in The Siberian Iris, Spring, 1994. Listed below are some irises reported to exhibit repeat bloom, at least in some circumstances. Asterisks indicate those reported to be more reliable. 
Again                   Blue Encore             Blue Forty
Butter and Sugar        Charming Darlene        Chartreuse Bounty *
Chilled Wine            Coquet Waters           Dancing Nanou
David Hebditch          Devil's Dream           Dreaming Yellow            
Early Bluebird          Echo Two                Eric the Red
Ever Again              Exchange                Exuberant Encore *
Fairy Dawn              Fine Tuned              Fourfold Lavender
George Henry *          Grand Junction          Harbor Mist                
Harpswell Happiness     Harpswell Prelude       Heliotrope Bouquet
Indy                    Invader                 Japanese White
Lavender Bounty *       Lavender Light *        Lillabelle
Lucky Lilac             Mad Magenta             Maggie Smith
My Love *               On and On               Outset
Percheron               Placid Waters           Purple Sand
Reprise *               Rimouski                Shirley's Choice
Snow Queen              Soft Blue *             Springs Brook *
Standing Tall           Summer Sky              Tiffany Lass
Violet Repeat           Visual Treat            Welcome Return *
White Encore            White Prelude           Wine Wings              
Wisley White
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