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Update on two "Iris Parking" sites.

June 19, 2020 Covington, La.

Gary Salathe and Destiny Simon of the Louisiana Iris Conservation Initiative (LICI) did a workday on Friday, June 19th collecting I. giganticaerulea irises from two locations. The I. giganticaerulea iris is one of five Louisiana iris species, four of which are native to Louisiana.

The irises were removed from two sites where they were planted as an experiment started five years ago to see if places could be found where they could grow without any maintenance. The plan was to have the irises grow in bogs that were found in various locations in St. Tammany parish so that they could be thinned out every other year to use in iris restoration projects. The process has been nick-named as "parking irises", in that they are only meant to stay in these locations as a way to grow them out to be used in future projects, not as a permanent home to be on display to the public.

The two volunteers thinned out irises from two clumps in each location and ended up with about 300 plants. These add to a total of about 1,000 irises that have been removed from the two locations over the last few years.

The first location is a "dry" detention pond for a subdivision near the Goodbee crossroads in western St. Tammany parish. The parish requires all rainwater runoff from new subdivisions to be funneled to areas like this, which are at the low point of each subdivision's drainage system located at its end. There is a choke point at the outflow of the detention pond so that it fills with rainwater from the subdivision during a heavy rain. A single culvert that drains the pond causes the water to be "detained" so that the water leaving the subdivision’s drainage system, as the detention pond slowly drains off, leaves at the same speed as it did from the land before it was developed. This keeps the waterways down stream from the subdivision from overflowing and backing up because of water rushing into them because the drainage of the land upstream has been improve by its being developed.

St. Tammany parish has hundreds of these detention ponds.

A "wet" detention pond is a pond that holds water, which is usually located within the subdivision where it can be seen to add to the beauty of the neighborhood. The ponds usually have a 3' - 4' high sloped bank to allow that portion to fill up during heavy rains and be "detained".

A "dry" detention pond, like the one shown in the photo, generally is in hidden areas of the subdivision and only hold a few inches of water that usually disappears during dry periods. However, each time there is a hard rain it will get replenished with new rainwater from the subdivision's drainage system.

Each year during one of the dry periods the parish will bush-hog dry detention ponds to keep trees and bushes from taking over. This is usually done when the irises are in their dormant period, so the theory from five years ago was that these dry detention ponds may be the perfect place to propagate species irises long-term without having to do any maintenance. You'd just let nature take its course!

Photo: Small clumps of irises can be seen with light green leaves out in the detention pond. They were planted last year. They had about 3" of standing water around them on Friday. They will likely need a couple more years before the clumps are large enough to thin out.

The plan for this workday was to thin out two clumps that were close to the pond bank.

The irises the two collected were still in their growth mode with new branches starting to come out from the center rhizome. Each clump that the irises were removed from were inspected during March when they were in bloom to confirm that they were the I. giganticaerulea iris that was planted there five years ago. The two clumps were last thinned out two years ago.

The second location is a transmission power line right of way where it was discovered five years ago that it had a small bog in its center. The bog was about 150' long and about 20' wide when the irises were first planted. After the first group of irises were thinned out a construction crew filled all but 50' of the bog. Luckily, most of the irises were removed from the area to be filled after the construction equipment showed up, but before they started work. Some irises were destroyed when there wasn't enough time to get them all out.

The 50' of bog that had been left was untouched for two years, so an investigation was launched this spring to see if any irises were still there. About 120 I. giganticaerulea iris were found happy and blooming!

The two volunteers took out all but about 30 irises so that the process can start all over again.

Photo: The surviving section of the bog is only about 10' wide, but it was still holding water after two weeks of no rain.

Photo: The irises were healthy and still in their growth mode.

Half of the 300 irises were planted, Saturday, June 20th, in the Bayou Sauvage wildlife refuge as a continuation of a project LICI has there. The other half were planted at the LICI iris holding area in New Orleans so that they can grow until they are used in projects this fall.



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