The Species of Louisiana Iris

Iris brevicaulis Iris fulva Iris hexagona
Iris giganticaerulea
Iris nelsonii
Iris brevicaulis Iris fulva Iris hexagona Iris giganticaerulea Iris nelsonii

Download a great article on Louisiana irises in the wild by Benny Trahan, Sr. from Fleur de Lis, the Society for Louisiana Irises' journal (1.5 megs). Also, a follow-up article in Winter 2008 on Benny's "find of a lifetime," his rediscovery of the yellow I. nelsonii (120k).

Take a look at the Louisiana Iris Species Preservation Project sponsored by the Society for Louisiana Irises and the Greater New Orleans Iris Society.


There currently are five recognized species in the Series Hexagonae, as the Louisiana iris group within the Genus Iris is called. They are: I. brevicaulis, I. fulva, I. hexagona, I. giganticaerulea and I. nelsonii.  

Although there is variation within each species, all are considered to have an identifiable ecological niche and unique characteristics.   Sounds simple, but as is usually the case in such taxonomical matters, there are questions and controversies at the boundaries.  Since species are categories imposed by humans, there inevitably are differences in how people would construct them.  

Species are rarely designated based on complete or perfect information, and it is possible that new evidence and especially new technology may lead to the combining of recognized species or the singling out of new ones.  In fact, some people already classify the species differently.  All those caveats aside, the current structure of five recognized species does its job of helping bring order to a complex iris world and assisting us in understanding the background of what we today call Louisiana irises.  

The individual species pages on the Zydeco web site will show nice and representative pictures, hopefully generate some interest, raise a few questions, and link to more detailed information and references.  


Louisiana irises are all related, of course, in being members of the same Series, Hexagonae, within the Genus Iris.  (The series name is derived from the first species in the series to be named, I. hexagona).  All the species will interbreed both in nature, given the chance, and under the prodding of the hybridizer.  Their natural ranges overlap only in limited areas, however  -  mostly, and perhaps only, in Louisiana.  In the years after the 1920s when these irises were "discovered", both botanists and iris enthusiasts systematically searched -- especially in Louisiana and Florida but also other states of the Gulf Coast -- for "new" irises that might be additional species.  Many differing colors and forms were found and named as species, but most turned out to be natural hybrids, mainly of I. fulva and I. giganticaerulea origins.  The work of Percy Viosca of New Orleans in the 1930s showed that there were only a few species that served as a foundation for many natural hybrids.

The Blues

The currently recognized species I. hexagona, I. giganticaerulea and I. brevicaulis (brevicaulis at one time was called I. foliosa) consist of irises in the blue-purple range with occasional white forms found.  Hexagona and giganticaerulea certainly share a surface similarity.  Some feel that these two should be regarded as the same species; more specifically that giganticaerulea should be considered a subspecies of hexagona, which was the first named.  At one time, I. hexagona was thought to occur in Louisiana, but now it is considered to be confined to the southeastern states of South Carolina, Georgia and, especially, Florida, where there are huge populations of blue irises.  Reportedly, hexagona is almost extinct in South Carolina, with most of its documented locations inundated by manmade lakes.

Despite an inclination by some to lump them together, there seem to be clear differences between hexagona and giganticaerulea with respect to size, bloom season and possibly other characteristics.  Giganticaerulea, as the name asserts - meaning literally "Giant Blue" - indeed is a giant, growing to 5-6 feet or more in the swamp; hexagona is much shorter.  Also, giganticaerulea is a relatively early bloomer and hexagona has a much later bloom period.   Still, put them side by side and the similarities of the flower are strong.  Proper classification is something for others to sort out and work needs to be done.

The other blue, I. brevicaulis, is distinctly shorter than either hexagona or giganticaerulea, and it is very definitely a late bloomer.   There is no confusing I. brevicaulis with the other blue species.  It has a pronounced zigzag stem and is found in damp but relatively more upland and northerly sites. Giganticaerulea and hexagona are inhabitants of the lower regions of the Gulf Coast states (except for some locations in South Carolina and Georgia), but I. brevicaulis occurs up into the Mississippi Valley states of Illinois, Ohio, and Kentucky.  

Florida Irises.  The native irises of Florida are a special case.  Most are considered to be in the Louisiana series, Hexagonae, and in the species hexagona, but evidence is emerging that there is more variation among these irises than previously acknowledged.  Michael Gideon has systematically observed Florida irises in the wild and reports variations in form that may invite reconsideration of their status as members of a single species.  Scientific work involving DNA testing is underway.  

Whether or not a new species designation is appropriate for some of the Florida irises, recognition of different forms certainly is. Many of the Florida irises when moved elsewhere do not thrive, for example, but others do grow well and produce the massive rhizomes characteristic of I. giganticaerulea when it grows in water.  Perhaps this suggests that Florida hosts multiple species, some well adapted only to Florida conditions.  While there are huge numbers of irises growing in Florida, the red species, I. fulva and I. nelsonii, are not there, except for a limited presence of fulva reported in the panhandle near Alabama.  For more information there is a Florida iris page here and you can download a three article series on the native "Louisiana" irises of Florida that appeared in the quarterly magazine of the Society for Louisiana irises.

The Reds

Louisiana iris enthusiasts are fond of asserting that Louisianas have the widest color range of all types of irises.  If so, it is I. fulva and I. nelsonii that deserve the the preponderance of credit, adding both red and yellow to the palate.  While hybridizers of other types of irises have strained and labored to produce red cultivars, Louisiana iris hybridizers had them available and growing in the ditches and swamps.

Like brevicaulis, fulva is found well up into the Mississippi Valley.  (It is probably the case that I. fulva and I. brevicaulis genes account for the hardiness of hybrid Louisianas across virtually the entire country).  I. nelsonii, on the other hand, has the most restricted range of any of the Louisiana group.  Also the last to be designated as a species, by Randolph in 1966, nelsonii occurs in a relatively small and agriculturally threatened area a few miles Southeast of Abbeville, Louisiana.  For years after their discovery in the late 30s by W. B. MacMillan, they were referred to as "Super Fulvas" or "Abbeville Reds."  Randolph concluded that the nelsoniis are a stable population of hybrid origin, worthy of species designation, and mainly based on fulva input but with genetic traces back to both giganticaerulea and brevicaulis.  The plants and flowers of I. nelsonii are much larger than fulva, and the swamp and wet woods of their limited range is not the most typical setting for fulva, which was not found in the immediate area.

Natural Hybrids

In Louisiana, where the natural hybridization between at least four of the species occurred  --  with their blue and white, red and yellow forms  --  a remarkable range of plants, wildflowers all, were available to jump start hybridization.  The modern hybrids are almost entirely derived from this Louisiana stock, and that is one of the reasons that the name "Louisiana irises" is apt, even for species that occur now and then in wet locals across much of the eastern part of the country and into the Midwest.  No less a figure than John James Audubon was the first to apply the "Louisiana" designation, with his depiction of I. fulva in his painting of the Parula Warbler.  Current hybrids are generally derived from all of the species, except for the East Coast species I. hexagona, which, so far, has been used hardly at all by hybridizers.  

Additional Information

For additional pictures, information and links pertaining to particular species, click on the pictures above.  If the subject is of interest, be sure to follow the links to the sites created by Rodney Barton and Dennis Kramb.  

Rodney Barton's North American Native Iris web site has excellent pictures and other information, including maps showing the geographic range of each species.

Dennis Kramb's species iris database was created for the Species Iris Group of North America (SIGNA).  Search by species name or page down and click on the Louisiana species in the list.  You might want to check out the main SIGNA web site, also.

The USDA Natural Resources Conservation Service maintains a plant database.  From this page, search by full name of species, for example, "Iris fulva" for information.  The site offers maps of distribution by state and in some instances by county within state.  Some of the information is incomplete or inconsistent with other sources, but interesting.

The USDA Forest Service has created a very nice site with pages on the wildflowers, including native iris species that grow on Forest Service land.  This is an excellent site for native plant and wildflower information, including extensive links to other sites.  The site's distribution maps of the Louisiana species are taken from the USDA Plants database and show I. giganticaerulea restricted to Louisiana and I. hexagona ocurring all across the coastal south and up into Missouri.  This is in contrast to the more widely accepted view in Louisiana iris circles that I. hexagona is restricted to the East Coast and I. giganticaerulea extends into Texas and Mississippi.  Compare the USDA maps to those on the Rodney Barton website listed above.

There are several good histories of Louisiana irises that weave together information about the species, the story of their "discovery" and the development of the modern hybrids.  For an online source, see Tom Dillard's Louisiana iris history from the Society for Louisiana Irises Newsletter, now renamed as the quarterly journal Fleur de Lis.  See also the Society's definitive book on Louisiana irises for a chapter on their history by Richard Goula.  In the second edition, Goula's history chapter from the first edition was repeated with slight modification but without attribution.  Also on the Society for Louisiana Irises web site, click here for species pictures and other information.  

Take a look at this LSU Library Special Collections site dedicated to the work of Percy Viosca, one of the important early figures responsible for sorting out the confusing array of Louisiana iris species and natural hybrids that were found in Louisiana.  You have to use the search feature to isolate Viosca's iris pictures, which are old, black and whites taken before 1935.  They include flower closeups and landscape pictures.  Other pictures on the site document scenes in South Louisiana recorded by Viosca, one of Louisiana's "preeminent naturalists."

Richard Sloan has created a series of beautiful pages on Louisiana irises and his Louisiana iris species page has both beautiful pictures and good information.  Be sure to follow the links at the bottom to see Dick's other Louisiana iris pages.

The Flora of North America website has an interesting iris page with technical descriptions to the iris species, including Louisiana irises, and links to distribution maps and illustrations.   The source is interesting in that it describes Iris savannarum, which was once included among the recognized Louisiana species.  The Flora of North Americal treats it as I. hexagona var. savannarum, and places it in South Florida, Southwest Georgia and Southeast Alabama. This overlaps I. hexagona, which this source shows as limited to a relatively small area of North Florida and the East Coast of South Carolina.  This view corresponds to the observations of some that there is more variation in the Florida irises than is supported by the one species, I. hexagona, generally attributed to the state.

Each individual species page on the Zydeco web site has additional links to information on the particular species.