IRISES HAVE GONE CAJUN

March 08, 2007

BY PAUL AND MARY MEREDITH - VICTORIA COUNTY MASTER GARDENERS

EDITED BY CHARLA BORCHERS LEON

Our first planting of Louisiana iris was in Georgia. A low spot in our yard was constantly wet. Nothing grew there except weeds. We had heard about and seen pictures of beautiful beardless irises growing in standing water. We ordered some and planted them in our swamp. They thrived with no fertilization and were cold hardy to the teens. Annually, when they bloomed in mid-March to May, folks who spotted them stopped to ask what those beautiful flowers were.

We first heard of them recommended for inter-planting with daylilies because of the difference in the two plants' blooming seasons. Whatever the reason, Louisiana irises can be welcome additions to a Southern garden.

LOUISIANA IRIS SPECIES

There are five iris species that are classified as "Louisianas:" I. fulva, I. hexagona, I. brevicaulis, I. giganticaerulea and I. nelsonii.

Each species' characteristics are listed in the table. You can identify them by their "beardless" characteristic; their blooms do not have prominent vertical parts. But they are quite diverse in color, height, growth patterns and growing locations and yield a beautiful and striking range of hybrids.

What they need

Louisianas' three most important cultural requirements are water, soil and fertility. They also all grow best with at least a half-day's sun during their growing season, September through March.

Water is probably the most crucial factor, but some hybrids grow in ordinary garden culture. And I. brevicaulis has been seen growing in flooded oyster beds, in very alkaline water.

Natural fertilizers such as manures and compost are preferred. Some clay in the soil reduces the soil's drying, and acidic inorganic fertilizers are important supplements. Louisianas can be grown in raised beds, with or without other kinds of plants; in standing water, such as in ponds; or in boggy-type conditions. And they can be planted in the ground or in containers.

Beds, pots and water

For irises in beds or containers not submerged in water, the soil should be moderately to strongly acidic, a maximum 6.5 pH. While tilling their beds, add acidifying ingredients, including manure, composted leaves, peat moss, decayed grass clippings and azalea and camellia fertilizer.

Water culture for Louisianas, on the other hand, can mean growing them in shallow ponds or on the edges of ponds. Or, you can grow them in pots or tubs, which have no holes. The pots can stand alone, like other plants' pots, be partially sunk into the ground, or be submerged in water. Containers sunk into the ground should have at least 2 inches of the container above ground level. Cultural requirements for containers standing alone or sunk into the ground are the same as for beds. But requirements for containers submerged in water differ. For containers submerged in water, the rim should be no more than 1 inch below water level, and their soil must be heavy clay.

Iris rhizomes

Louisianas grow from rhizomes. These should be planted in late summer after the dormant season (mid to late summer) as the growing season begins. Planting at other times is not recommended in our hot climate. Follow the supplier's planting instructions.

The rhizome should be planted deep enough for the roots to be spread and the top of the rhizome covered with soil no more than an inch deep. Make a small mound of soil in the hole and spread the roots around the mound. Plant firmly, and water thoroughly.

Louisianas like to spread. The closer you plant their rhizomes, the more often you will have to dig and replant them. Rhizomes planted 12 inches apart need replanting every two years. These irises perform best when fertilized in October, December and February with a balanced fertilizer, such as 8-8-8 or azalea and camellia fertilizer.

Watering

It is not possible to water Louisianas too much. Plants must be watered in the growing season and after the blooming season. If a good rain does not occur once a week in summer, give the plants a good soaking. About 2-3 inches of acidic mulch, such as pine, helps keep the plants cool. Getting them too hot stunts their growth and harms the next season's bloom.

Irises grown in submerged tubs need their water level maintained at 1-5 inches below the surface. Water depths over 5 inches causes rot.

Hybrids

                                                                                PHOTOS CONTRIBUTED BY HEATHER AND BERNARD PRYOR
The diversity of colors and forms among hybrids of the five native species of Louisiana iris is extraordinary. Shown here are three crosses by master hybridizers Heather and Bernard Pryor of Iris Haven in Sydney, Australia.

An entire column could be dedicated to hybridization. We'll just describe briefly the diversity available to use. Plants can range from 1.5 to 5 feet tall with growth habits from clumps of landscaping plants to showy solo plants. And the colors are gorgeous.

Louisianas' genetic diversity produces whites, yellows, apricots, blues, purples, pinks, lavenders, reds, variegated, bi-colors, even in fringed and frilly forms.

For more information

If you want to more information about these showy plants, visit the Society for Louisiana Irises (SLI) Web site, http://www.louisianas.org/. Members get a marvelous publication and have great meetings. SLI also publishes a book, "The Louisiana Iris," now in its second edition. To find sources of plants, you can search the Web or visit the Victoria County Extension Office to view a recent SLI newsletter listing some sources.