Louisiana Swamp Iris: Garden Treasure of Gulf Coast Swamps

Summary: The native Louisiana swamp Iris is a brilliant star of the floral world, admired for its airy grace and beauty but too often unappreciated as a suitable garden subject.

One of the most brilliant stars to blaze across the floral horizon over the years is the native Louisiana swamp iris. For centuries this native Louisiana iris has been a resident of Gulf Coast swamps and bogs, admired for its airy grace and beauty but unappreciated as a suitable upland garden subject.

louisiana swamp irisPin

True, a few pioneer collectors found rare specimens and gave them garden culture. But it took the publications of the eminent botanist John K. Small, who explored Louisiana’s iris fields during the 1920s, to bring these wildings to the attention of flower lovers throughout the country.

Today, Louisiana iris are enjoyed in thousands of gardens from the Atlantic to the Pacific and Canada to the Gulf.

Annual Trek for Collectors

There was a time when ardent collectors would make an annual trek to swamps in search of new iris varieties each spring. Over time, many learned the art of cross-pollination and methods of germinating the seed.

As a result, most collected clones are natural hybrids, and great variation is obtained with Iris plants grown from open-pollinated seeds. 

John Small named and described nearly 100 clones of swamp irises he discovered and presumed to be species. Still, the varieties which have been named and registered with the American Iris Society over decades and the unnamed seedlings in gardens of amateur breeders are legion.

Four Main Types Of Louisiana Swamp Flowers

There are four main types of iris flowers native to Louisiana swamps. One of these, Iris virginica, which grows in low places in pine flats, cannot be claimed exclusively by the state since it and related forms are found widely scattered from the Great Lakes to the Gulf.

The strap-like leaves are 24″ to 30″ inches in height, with pale blue flowers showing just above the top of the foliage. Occasionally a white-flowered form will be found, and even more rarely, a light lavender to pink.

Iris virginica has not been successfully crossed with other species and varieties of the “Louisiana’s.”

The magnificent, tall blues of the coastal marshes, just above brackish water, are the species Iris giganticaerulea. They are dubbed C. C.’s for short by native fans.

The flower stapes are frequently 5′ to 6′ feet tall, with huge blossoms which rival or surpass the Japanese iris in size. In addition, color mutations have been collected with flowers of white. These are greatly prized and increased in upland gardens.

The bronze or flame-colored found in alluvial lands of the Lower Mississippi Valley. Colors range from light pink through the coppery shades to an almost true red. A pure yellow is sometimes found, and this is a prize discovery to be experienced by the collector, possibly only once in a lifetime.

On the bluff lands or second terrace soils of the Mississippi River, one finds a hardy race of dwarfs with light blue and white flowers more rarely. The plants grow about a foot in height, with flowers borne down in the foliage on zig-zag stems.

Since Iris foliosa is most representative of the type, these low-growing dwarf varieties are referred to as foliosas.

Natural Louisiana Swamp Iris Crosses

When the tall blues, the flame-colored fulvas, and the dwarf foliosas are found growing in the same area, nature goes to work with the aid of the bumblebees and orioles to mix her colors. The vast number of resulting hybrids formed through the centuries are collectively called Louisiana native iris.

However, the clones vary widely in color, size of flowers, size and vigor of plants, and blooming habits. When red is mixed with blue, one obtains some purple flowers. And so, if the blue flowers of tall Iris giganticaerulea or dwarf Iris foliosa are crossed with the red or rust-colored Iris fulva, purples are obtained.

The old variety, DOROTHEA K. WILLIAMSON, is a cross of Iris fulva with Iris foliosa, which probably accounts for its hardiness and popularity in northern gardens. The reddish-purple VINICOLOR was considered a seedling of Iris fulva x Iris giganticaerulea.

When yellow and white are introduced, there is an unlimited number of combinations that could result in the progeny of three distinct species and four separate colors. An interesting color form is found in the bicolors, with standards of one color and falls of another.

Great variation is found in the size, shape, and color of the signal patch or marking on the crest of the falls. This is usually some shade between light yellow and rich gold and may take the form of a line, a dagger, a steeple, or radiating lines.

The Louisiana native iris have a very definite place in gardens in the lower tier of southern states where there is not enough cold weather for satisfactory performance of their tall, bearded iris cousins. Further North, where they are forced into dormancy during winter months, the growth is not so luxuriant, and the flowering is less profuse.

Humid Climate, Fertile Organic Soil Required

Live in a humid climate anywhere between Wisconsin and Texas or between Massachusetts and Washington. You may enjoy the beauty of these native Southland plants and grow them without bog or pond culture.

You’ll need deep, fertile soil, full of organic matter, and high in the essential elements of plant food, namely, nitrogen, phosphorus, and potash.

Manure, compost from rotted leaves or other vegetative materials, or peat moss are highly satisfactory if used in sufficient quantities. A mulch about 2″ inches deep is needed in the North for winter protection and throughout the entire country to protect the rhizomes from the heat of the sun.

Louisiana iris are not subject to bacterial rot of the rhizomes, but sunscald during July and August may cause heavy losses.

Sawdust, crushed corn cobs, peat moss, cottonseed hulls, rice hulls, sugar cane bagasse, or even leaves and straw may be used effectively as mulching materials. Lastly, use the garden hose generously during drought.

by C Davis