Vast stands of wild Louisiana irises — vibrant purple, blue, red, yellow and orange flowers that thrive in the wet, swampy state — have been replaced by roads and buildings, leading to concerns that they are running out of habitat. A small group of enthusiasts is doing its best to make sure that the widely varied group of plants doesn't go the way of the passenger pigeon.

The Society for Louisiana Irises launched the Louisiana Iris Species Preservation Project three years ago to create repositories in at least seven different locations for a large number of wild iris varieties, which also have been threatened by farming, flood management, oil work, illegal dumping and natural disasters.

"That's part of the reason for establishing those collections now," said Charles Perilloux of Baton Rouge, who heads the preservation effort that started in 2015.

Hurricanes and saltwater intrusion in the marshlands already have wiped out some varieties in the wild, though they have survived in gardens, Perilloux said.

Four repositories have been established so far. The biggest, under the care of the Greater New Orleans Iris Society, is in New Orleans' City Park. Perilloux tends a repository in Baton Rouge. The other two are in Livingston, Louisiana, and Cleveland, Tennessee.

A woman in Ohio, where one species is native, has agreed to take on stewardship of a fifth collection in Rushsylvania, about 45 miles (70 kilometers) northwest of Columbus, Perilloux said. He is trying to find at least two more stewards, preferably one in Texas and another in Florida or South Carolina.

In New Orleans the plants are in 7-gallon (25-liter) plastic pots grouped in 10-to-20-foot-long (3-to-6-meter-long) timber-and-plastic retaining ponds so their roots stay moist. Several plants often grow in one pot. One species, Iris gigantacerulea — Louisiana's state wildflower — is so big, each variety is in a separate kiddie pool. The Baton Rouge location is in Perilloux's yard, where floating docks hold scores of pots with their bases in a half-acre pond.

Since irises spread through underground stems called rhizomes, they're in labeled pots to keep them separate. "If you have them in the ground, the rhizomes will spread and you lose track of which variety is where," Perilloux said.

There are about 280 species of iris in the world, 28 of them native to the United States, according to the U.S. Forest Service.

The five species known as Louisiana irises — four of them native to Louisiana — can hybridize with each other but not with any other species, Perilloux said. Two of those five species can be found in more than a dozen other states, and one of them grows as far north as southern Ontario, Canada. The fifth species once grew in Alabama, Florida, Georgia and South Carolina, but is increasingly rare and may now exist only in Florida, Perilloux said.

Within the five species, more than 100 varieties have been found in the wild. Many are so different from each other that a renowned botanist of the 1930s thought there were more than 100 species, at a time when only 18 species of iris were known to exist in North America.

One species that is particularly in danger is the "Abbeville red," which also comes in yellows and oranges. It has been found in the wild only in one small cypress swamp that has fared poorly since its discovery in 1938. Problems there include herbicides from nearby farms and rice hulls being dumped into the swamp, Perilloux said.

The preservation project is winning praise from other conservationists. Peter Raven, president emeritus of the Missouri Botanical Garden, called it unusual and magnificent.

"We've all urged private individuals and private groups to do this sort of thing," he said.