Most Louisianans are probably at least familiar with the term “Louisiana iris,” though fewer may be familiar with the five species of Louisiana irises, four of which grow wild in our state. Any naturalist in Louisiana ought to become familiar with our state wildflower Iris giganticaerulea and its close relatives (I. fulva, I. nelsonii, I. brevicaulis, and I. hexagona).
Louisiana irises, considered by many to be any of the five species in the series Hexagonae within the genus Iris, can hybridize and produce fertile offspring and are native various portions to the eastern and central United States. Louisiana irises and their hybrids are extremely popular among gardeners in the US and abroad. Their ability to grow both in water gardens and conventional garden beds and wide variety of colors have contributed to their popularity.
In South Louisiana, Louisiana irises begin growth with the arrival of cooler temperatures in the fall. Their upright green leaves provide a nice splash of color in the dead of winter. Around mid-March, flower stalks begin to rise and Louisiana irises bloom from mid-March through April and May, depending on the species and variety. In a study of I. fulva and I. brevicaulis (and their hybrids), the most numerous pollinators included American bumblebees (Bombus pennsylvanicus) and Ruby-throated Hummingbirds (Archilochus colubris).2 In Louisiana’s marshes, the large, early flowers of Louisiana irises can be an important nectar and pollen source for these large pollinators.
Iris giganticaerulea, as you may deduce from its scientific name, is also called the giant blue iris.3 This is Louisiana’s state wildflower and likely the most common iris you might find in the freshwater marshes and swamps along Louisiana’s gulf coast. It’s the largest Louisiana iris and produces flowers 5 inches across and anywhere from 4 to 6 feet tall.4 This species is only found along the gulf coast of Texas, Louisiana, and possibly Mississippi. The giant blue iris is considered globally vulnerable (G3), though it can be abundant locally.
Iris fulva, the copper iris, is a much smaller Louisiana iris and naturally has rusty red flowers.3 This iris usually has flowers 3–4 inches across and about 3 feet tall. The copper iris grows predominantly within the Mississippi River drainage up to Kentucky, Ilinois, and Ohio down to Louisiana and Mississippi. It has contributed red color and cold tolerance to many Louisiana iris hybrids produced by breeders.
Iris brevicaulis, the zig zag iris, is the smallest Louisiana iris.3 Unlike the other Louisiana irises, you won’t find it in swampy or marshy areas. The zig zag iris naturally grows in uplands along the Gulf Coast up to Missouri, Kentucky, Ohio, and Illinois, and is even found in Ontario though it’s endangered there. The zig zag iris has been used extensively in hybridization to impart cold tolerance and its unique zig zag form.
The Abbeville red iris, Iris nelsonii, was a sensation among Louisiana iris enthusiasts in 1938.3 Fittingly, this swamp dwelling, tall red iris was sometimes called the “Super Fulva.” This iris has more intensely red flowers than I. fulva and the flowers are about 5 inches across and 3-4 feet tall. As in the name, the Abbeville red iris can only be found naturally in the Abbeville area. Research over the years has shown that I. nelsonii is a species of hybrid origin withgenetic traces of I. giganticaerulea, I. fulva, and I. brevicaulis. Since all natural stands of I. nelsonii are on private lands, a protected colony has been established at Palmetto Island State Park in Abbeville by the Louisiana Department of Wildlife and Fisheries. It is considered imperiled (S1) in Louisiana.5
The fifth Louisiana iris (Iris hexagona, the Dixie iris) doesn’t naturally occur in Louisiana, but it does occur in Mississippi, Alabama, Georgia, South Carolina, and Florida.3 This species is somewhat similar to the giant blue iris. Its flowers are generally white, light blue, or blue and about 4.5 inches across and about 4 feet tall.
Louisiana irises are, and should be, considered one of Louisiana’s native charismatic species, though their identity has become a bit muddied with the prevalence of hybrids in the nursery trade (and the confusion of calling the invasive Iris pseudacorus a Louisiana iris when it is not). With the unfortunate trifecta of coastal marsh subsidence, saltwater intrusion, and hurricanes, Iris giganticaerulea is now hard to find in the coastal marshes where it once was common.
The disappearance of these and many other unique forms of wild Louisiana irises led to Charles Perilloux and the Greater New Orleans Iris Society to create the Louisiana Iris Species Preservation Project.6 This project’s goal is to preserve the genetic diversity of the five Louisiana iris species. This and other projects such as the “A Louisiana Pond” project7 are working grow unique irises, promote them among the public, and eventually reintroduce irises to protected habitats within their native ranges.
To ensure that future generations also grow up around our state wildflower, master naturalists across Louisiana can use their collective voices to advocate for the wetland habitats that Louisiana irises need, grow species irises, volunteer in iris rescue projects, and volunteer at wetland restoration projects.
Musacchia, Joe. 2015. Understanding Louisiana iris, part 1: Iris giganticaerulea. World of Irises: Blog of The American Iris Society. https://theamericanirissociety.blogspot.com/2015/03/understanding-louisiana-iris-part-1-i.html.
Musacchia, Joe. 2015. Understanding Louisiana iris, part 2: Iris fulva. World of Irises: Blog of The American Iris Society. https://theamericanirissociety.blogspot.com/2015/06/understanding-louisiana-iris-part-2-i.html.
Musacchia, Joe. 2015. Understanding Louisiana iris, part 3: Iris brevicaulis. World of Irises: Blog of The American Iris Society. https://theamericanirissociety.blogspot.com/2015/08/understanding-louisiana-iris-part-3.html.
Musacchia, Joe. 2015. Understanding Louisiana iris, part 4: Iris nelsonii. World of Irises: Blog of The American Iris Society. https://theamericanirissociety.blogspot.com/2015/10/understanding-louisiana-iris-part-4-i.html.
Musacchia, Joe. 2015. Understanding Louisiana iris, part 5: applying what we learned to modern cultivars. World of Irises: Blog of The American Iris Society. https://theamericanirissociety.blogspot.com/2015/12/understanding-louisiana-iris-part-5.html.
On January 6, a strong cold front moved through Louisiana, bringing the coldest temperatures we’ve seen since at least 2015. Shortly before the front, I came across an article from the Lady Bird Johnson Wildflower Center about frostweed (Verbesina virginica) (Schwartzman 2017). Frostweed is one of a handful of plant species that exhibit the process of crystallofolia.
Crystallofolia, or ice flowers, is the process in which water is drawn up through the roots and through the stem of a perennial plant forming ribbons of ice during the first few hard freezes of the year (Harms, crystallofolia). The process through which this occurs is known as ice segregation, where above-freezing and below-freezing temperatures are juxtaposed (Carter, ice segregation). Only a few species of native plants in North America are known to produce ice flowers regularly among wild-growing populations. Among these are stone mint (Cunila origanoides), longbranch frostweed (Helianthemum canadense), frostweed (V. virginica), and sweetscent (Pluchea odorata).
Hard freezes are rare in south Louisiana, so I decided that the morning of January 7 was the perfect opportunity to see crystallofolia for myself. After I described this phenomenon to Samantha, my fiancée, she decided to join me. I knew of a small patch of sweetscent within about a minute of the Tuten Park parking lot, so it would be easy to see the ice flowers and get back to the car if it turned out to be too cold for us.
We made it out to the park at about 7:10 AM, and it was 25°F. I’m only familiar with sweetscent when it is flowering. In January, it was obviously dormant and looked like every other brown, dormant plant in the area to me. We looked over a few similarly sized plants and found no ice flowers. Then, we saw some white. As we moved closer, we could see a little patch of three sweetscents, each with an ice flower at its base. We crouched down in amazement, and I photographed them. Each ice flower was about 5 cm wide and about 3 cm tall. They were a lot thicker than many of the ice flower photographs I had seen online, but most of those are photographs of either stone mint or frostweed.
Then we walked away to look at my planter box near the back gate of the park. It contains a mixture of native and non-native high-value pollinator plants. To my surprise, the tropical sage (Salvia coccinea) had also formed an ice flower. This was all along the lower foot or so of the stems of the largest plants. It had formed as if the water in the stem quickly cooled and a slow-motion explosion of ice occurred. This sighting was completely unexpected to me as I hadn’t read anything about this species of sage producing ice flowers. Later, I found a resource describing a crystallofolia-like process in cultivated tropical sage (Harms, Salvia coccinea). We continued our trek to the back of Tuten Park and observed no other ice flowers. Actually, the temperature seemed to rise as we entered the woods and seemed much warmer around the shoreline of the pond, a good example of a microclimate.
There are several very good internet resources about crystallofolia and ice flowers, each from a different perspective. First, I’d encourage everyone to read the ice flower article that was featured in American Scientist (Carter 2013). Dr. Bob Harms put together an outstanding website about crystallofolia from a botanical perspective and from his observations in central Texas. Dr. Harms passed away in October 2016 and was a linguistics expert who transitioned to botany as Professor Emeritus. Dr. Jim Carter has a great website about many facets of ice, including ice segregation and ice flowers as well. I corresponded with Dr. Carter when compiling this article and his input was a big help in understanding the crystallofolia process. There is more information about ice flowers than I could include in this article since I also wanted to provide a narrative of my own ice flower observations. Visit Dr. Harms and Dr. Carter’s websites as they provide a wealth of information about this and other plant and ice segregation products.
Carter, James R. 2013. Flowers and Ribbons of Ice. American Scientist. 101: 360. http://www.americanscientist.org/issues/feature/2013/5/flowers-and-ribbons-of-ice/1
Carter, James R. Ice Segregation. Personal Webpage. http://my.ilstu.edu/~jrcarter/ice/segregation/
Harms, Bob. Crystallofolia (‘Frost Flowers’), with stems of frostweed (Verbesina virginica) & marshfleabane (Pluchea odorata). Personal Webpage. http://w3.biosci.utexas.edu/prc/VEVI3/crystallofolia.html
Harms, Bob. 2008. Salvia coccinea (Scarlet Sage), as a candidate for crystallofolia. Personal Webpage. http://w3.biosci.utexas.edu/prc/VEVI3/SACO5.html
Schwartzman, Steven. 2017. The frost below. Wildflower News. Lady Bird Johnson Wildflower Center. https://news.wildflower.org/the-frost-below/
Volunteer for a Christmas Bird Count!
Christmas Bird Count is taking place all over the state. Get out there and VOLUNTEER for one or more Christmas Bird Counts. This is a great way to earn volunteer credit and perform some very important citizen science. The Christmas Bird Count is a valuable source of data that helps with conservation efforts. See you at one of the Counts!
SLMN President' said:
Finally the cooler weather has reached Louisiana, and it’s much easier to get outside. We’re getting close to Christmas Bird Count (CBC) season, and I want to encourage everyone to get out and take part in at least one CBC. Don’t worry if you don’t know your birds! CBC compilers generally pair inexperienced birders with experienced ones so you won’t be thrown to the wolves. It’s really easy as a naturalist to get caught up gathering data for all sorts citizen science projects. Remember to just go out there and observe nature for yourself also. The easiest way to improve your naturalist skills is to go outside, observe organisms, and take notes (draw them too if you’re willing or able). I’ve had weeks or months pass without doing any birding that wasn’t related to my job or some other obligation. After a while of feeling stuck in a rut, I realized that I hadn’t been out birding for fun in ages. For me, birding is a restorative activity, and I bet being out in nature similar for many of you. So, please take part in citizen science (iNaturalist, eBird, Christmas Bird Count, etc.) But remember to go out there and observe for fun. Make notes and progress in your naturalist skills. You can always submit your observations to iNaturalist or eBird after the fact!
See ya’ll in January
SWLA Master Naturalists talks