Louisiana Iris: A Southern Floral Icon

The Louisiana Iris adds color, intrigue and history to water gardens everywhere.

Ships Are Sailing

These frilly purple petals and sepals belong to the Ships Are Sailing tetraploid variety.

iStockphoto.com/SondraP

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Throughout the Western world, the most recognizable floral icon is perhaps the fleur-de-lis, literally “flower of the lily.” Traced back at least to the 12th century, the classic, elegant design of the Louisiana Iris is thought to depict a stylized iris flower. Historically, the emblem was associated with the coats of arms and flags of French royalty, as well as the Trinity and Virgin Mary of the Roman Catholic Church.

Over time, the fleur-de-lis has evolved as an enduring symbol of early France and Christianity, as well as a metaphor for nobility, heraldry, artistry, perfection, purity, light and life.

Since I call Louisiana home, the fleur-de-lis has been part of my heritage, too. We Louisianians adorn everything from ornamental iron, tile and glass works to street signs, flags, stationery, clothing, Mardi Gras masks and those stylish helmets of the New Orleans Saints football team with the fleur-de-lis. Moreover, in 1990, the Louisiana State Legislature adopted as the official State Wildflower an actual living fleur-de-lis: the Louisiana Iris. 

Irises abound

Irises are distributed worldwide, particularly within temperate climates. A special variety, however, occurs naturally only in the freshwater wetlands within the lower Mississippi Delta and along the Gulf Coast. Termed Blue Flag, Louisiana Flag, Louisiana Iris or simply, Louisianas, the names apply technically not to one but to five distinct but closely related species of plants with characteristic sword-like leaves (“flags”) and lily-like flowers. The Giant Blue Flag, or Iris giganticaerulea, largest and most common of the group, is honored as Louisiana’s official wildflower.

When nature ruled, southern Louisiana boasted one of the grandest spectacles of spring color to be found in North America. Early botanical chronicles describe the watery land of what is now the New Orleans Metropolitan Area as a kaleidoscope of color. As a youngster growing up in the outskirts of New Orleans, I remember seeing what my father called “Blue Flags” virtually everywhere rain and floodwaters lingered. Today, drainage and pollution of wetlands, coastal subsidence, erosion, incursions of saltwater, herbicides and exploitation by collectors have all contributed to a drastic decrease of these plants in the wild.

The five species that constitute the generalized Louisiana Iris share distinctive traits. For example, all require temperate climates with moist, acidic soils. Southern Louisiana – with its high rainfall, frequent hurricanes, and low topography featuring a labyrinth of swamps, marshes, bayous, rivers, and man-made canals and ditches – is the plants’ quintessential home. Individual specimens are usually 2 to 3 feet tall, although records document titans of 5 to 7 feet. The blade-like foliage springs from a fleshy, shallow underground storage stem called a rhizome. The plants propagate both by seed and perennial rhizomes, the latter being responsible for the dense clumping habit of the plants. From late March to mid-April, a mature plant will send up a thick bloom stalk, often branched, supporting five to 10 large flowers (3 to 7 inches across) that open sequentially, each lasting only two to three days. 

Provocative blooms

The flowers are what make the plant so provocative. The three petals and three sepals, often similar in color, are organized as two alternating whorls. A whorl is a biological term that refers to a set of petals going around the vertical axis of a flower. Each can range from upright or flaring to even arching or pendant. Furthermore, the flower may be augmented with an unusual third whorl: either flared styles (a style is the elongated part of the female pistil) or petaloids (extra petals) that vary in length and often sport elaborate crests. Double and semidouble flowers also are produced.

All floral parts are “beardless.” This means that the inner midline of each petal lacks the upright hairs or “beards” characteristic of most European or Asiatic varieties – the species most commonly marketed in plant catalogues.

Finally, the colors of Louisianas eclipse those of all other varieties. The palette ranges from pure white and yellow to blue, lavender and violet, as well as orange, rust and red. Appropriately, in Greek mythology, Iris was the female deity who transported messages between the Earth and the heavens. She was symbolized by the rainbow and referred to as “Goddess of the Rainbow.”

Upping the ante, in 1973, a retired research chemist, the late Joseph K. Mertzewiller, discovered how to give Louisiana Irises an auspicious genetic makeover. He accomplished this by exposing seeds to colchicine, a poisonous alkaloid originally extracted from the roots and seeds of the autumn Crocus or Meadow Saffron plant.

In certain plants, colchicine interferes with basic cell division, resulting in genetic anomalies called tetraploids (simply put, the plants have double the amount of genetic material – think chromosomes and DNA). More than 30 true-breeding tetraploid varieties of Louisiana Irises have been created; all produce flowers that are extraordinary in both form and color, and all are registered and marketed.

Gardeners might presume that these plants, which are native to the topsy-turvy wetlands of the Deep South, would prove finicky to cultivate elsewhere. Not so. The severe conditions of the natural habitat have genetically predisposed Louisianas for an unusually high tolerance to diverse environments. For good measure, individual plants are relatively resistant to pests and diseases. As a result, these hard-knock irises are prized and cultivated successfully in private and public gardens throughout the world. So, although Louisiana loses more wetlands each year than any other state, we natives know that the future of our regal – and natural – fleur-de-lis is secure.

Fleur-de-lis garden care

If aesthetics and patriotism woo you to garden with Louisiana’s technicolor fleur-de-lis, here are some suggestions:

  • Plants must be watered methodically, particularly during summer and early fall when the plants are relatively inactive.
  • Rhizomes must be heavily mulched all year to avoid scorching by summer sun and freezing during winter.
  • Plant in venues that include at least a half-day of sunlight and acidic soils (pH 6.5 or lower).
  • In autumn, fertilize heavily with manures, compost and/or acidic commercial preparations.

Louisiana irises are a natural for water gardens, either in a container or in-ground pool. Follow these simple tips:

  • Keep water level no greater than 4 to 8 inches above the rhizomes during the summer.
  • Drop the water to ground level each fall since rhizomes will rot if submerged for the full year.
  • Since the irises have a limited blooming period, enhance the water garden with a combination of summer and fall blooming aquatics (waterlilies are perfect). The verdant, upright foliage of the irises then acts as backdrop in a tableau that enables the plants to be enjoyed long past their spring dazzle.

Gary Noel Ross, Ph.D., is a professional butterfly ecologist who often tracks the swamps and marshes of his native Louisiana to research and photograph unusual aspects of nature.