The Louisiana iris adds a splash of bright purple to your garden. The golden highlights of the blooms are just the icing on the cake. Many flowering plants have stunning flowers, but few match the velvety and vigorous blooms of the Louisiana iris. They grow best near streams, ponds, and water gardens. When you grow it with other perennials and shrubs, you will still have unique landscapes in your garden even when the iris goes into dormancy.
Many gardeners grow the Louisiana iris not just for its ornamental values, but also because of its many benefits. These bright blooms attract pollinators such as monarch butterflies and bees among others. It’s no wonder that the Louisiana iris has won many awards including the Mary Swords DeBallion Medal and has a society dedicated to its growth and success.
Louisiana Iris Facts
Sometimes known as water iris or American swamp iris, the Louisiana iris (Iris louisiana) is a perennial that grows in clumps. As the name suggests, it’s a native of the Southeastern United States and has unique foliage. The leaves of the water iris are long and thin just like swords. They are often dark green and shimmer in the sun.
In the late spring or early summer, blooms open up and transform your garden immediately. The flowers are about 4 to 6 inches in diameter and come in many colors. Depending on the variety you grow, the flowers could be purple with golden highlights, white, yellow, pink, blue, or red. The blooms grow on thin stalks allowing them to sway in the slightest breeze and create quite a spectacle in your garden.
But you don’t have to have a creek or even a water garden to grow this water iris. It grows just as well in a pot, a garden, or even in a waterlogged bog. At a time when most plants struggle in wet soil, the American swamp iris enjoys getting its feet wet. This is why they thrive near waterways and if grown in soil, they need copious amounts of water. Some gardeners grow the water iris in a pot and place it in shallow water.
Louisiana Iris Varieties
The Louisiana iris has five distinct species that you can grow in your garden. Each one has unique features from the color of the flowers to the way you grow them. Some varieties can handle the full sun while others are sensitive to the light. Here are the 5 species of the water iris.
- Copper Iris (Iris fulva): Famous for its breathtaking red flowers that towers over 3 feet. This popular species is often found in ponds, marshes, and swamps. It can even tolerate saltwater and shaded areas making it the perfect plant for types of soil and growing conditions.
- Iris brevicaulis: This dwarf species only reaches about 16 inches when fully grown. As such you can grow it in a pot and keep it in a small space. It doesn’t need as much water as the other varieties so it’s easy to care for. The small flowers are either white or lavender in color.
- Giant Blue Flag Iris (Iris giganticaerulea): Another species that loves the water more than dry land. It grows for up to 6 feet and has bright velvety flowers that are either white or blue. It grows well in marshes and bogs so you’ll need to grow it near a water source. If you plant it in a pot, place the pot in shallow water.
- Iris hexagona: This variety is also a fast grower that loves the banks of lakes and ponds where it can get its fill of water. They also reach 6 feet high when fully mature. The flowers of this species are often purple with yellow highlights around the edges.
- Abbeville Reds (Iris nelsonii): A native of Abbeville, Louisiana, this species has red blooms that take center stage wherever you grow them. But some cultivars have yellow, white, and even brown flowers as well.
How to Grow the Louisiana Iris Plant
As a hardy perennial the water iris has USDA hardiness zones between 4 and 10. This allows them to grow in different regions regardless of the weather. Only freezing climates would stop this iris in its tracks. Other than that, this perennial grows in different types of soil and doesn’t require much experience on your part. Here’s how you’d grow the Louisiana iris in simple steps.
- One of the easiest ways to grow this iris is from fresh seeds. After the flowers bloom, seeds will grow pods. Once the pods become yellow, they’re ready to harvest.
- Give the seeds the water test to make sure they’re good. Get rid of any seeds that float since they won’t germinate.
- Place the seeds in a container full of water and let them soak for about three days. This makes it easy to peel off the outer shell.
- Choose a clay pot with plenty of drainage holes at the bottom. Depending on the variety you grow, you might need to place the pot in water so the holes are necessary.
- Prepare your potting mix. Experts recommend you use rotting manure and sand in equal portions for the perfect mix for the iris.
- Dig a small hole in the soil and plant the seed about half an inch deep. Cover with soil
- Water the soil making sure it gets thoroughly soaked. You’ll know it’s wet when you see water flowing out of the drainage holes.
- Place the pot in a shaded place and keep the soil moist until the seeds germinate.
- It will take between 3 to 4 months for the seeds to germinate.
- Once the seedlings grow leaves, you can take them outdoors. Keep them in a sheltered place from the chilly wind.
Louisiana Iris Care
It takes time and patience to grow the Louisiana iris. Germination usually takes months and the seedlings have a rather slow growth rate. Due to the unique conditions that these perennials require, caring for them can be a little challenging. This has to do with their voracious appetite for water. But it’s not just irrigation that needs your attention.
For a plan that can tolerate acidity and even saltwater, you won’t have trouble growing and caring for the Louisiana iris. That said, you should test your soil before you plant this iris to make sure the pH level is not very extreme. Also depending on what species you grow, you might have to keep the soil as wet or ever waterlogged as you can. Check the varieties section above to know which species need more water than the others.
Most varieties of water iris flourish in the full sun. They enjoy being flooded with light and the more hours of sunlight they get every day the better. On average you need to give them anything between 6 to 8 hours of sun a day. This doesn’t mean they have to be outdoors all the time. You can place the pot on a window sill facing the south or west to get enough hours of sunlight. In the summer months, you should keep the plants in a shaded area away from the glare of the sun.
The unusual needs of this iris for water make irrigation quite difficult sometimes. For one thing, most species of this iris don’t tolerate drought that well. Maybe your water iris can go without water for a short time. But soon it will show signs of struggling as the leaves turn yellow and soft and might even droop and fall. You don’t want to wait for the plant to scream for water like that. You need to make it a weekly chore to irrigate your Louisiana iris. And when you water it, the soil should get soaked. If your variety needs plenty of water, it might be easier to place the pot in a container filled with water.
Mulch and Fertilizing
Another way to improve water retention in the soil is to cover it with mulch. Mulch protects the soil against chilly weather and keeps bugs and insects at bay. Since the rhizomes of the water iris grow above the soil, a thick layer of mulch offers protection against the sun, chilly weather, and fungal infestation. Use pine needles as mulch for the best results.
As for fertilizer, you should use an 8-8-8 fertilizer and apply it twice a year. The first is in early spring to encourage growth. The second application is about 8 weeks before the flowering season. Avoid fertilizers high in nitrogen since that has an adverse impact on flowering and leads to denser foliage instead.
Pests and Diseases
Since the Louisiana iris grows in bogs, marshes, and waterways, you can expect it to attract plenty of pests. They come in all shapes and sizes. From snails and slugs to moles and voles. Snails can be a really big problem since they target the blooms of the iris and feed on the soft petals of the flower. For an ornamental plant, this can be a disaster. Moles and voles feed on the juicy rhizomes and even roots. One way to get around that is to bury the rhizomes in the soil to prevent the voles from reaching them.
As for diseases that afflict the Louisiana iris, there are three main infections you need to pay attention to.
- Rust: Leaves and stems show symptoms of rust as brown circles with yellow margins. It can be fatal to the plant if you leave it without treating the infected areas. Rust is often caused by nitrogen in fertilizers. Hold back fertilizing and wait for the plant to recover.
- Leaf Miner: This infection shows on leaves as white blotches of color. Eventually, the leaves will collapse and fall out. The larvae of a certain fly cause it and you need to remove the infected leaves to prevent the spread of the disease. That way you won’t have to use herbicides to fight it.
- Iris Borer: A type of worm that feeds on the leaves and blooms of the iris. It drills holes in the rhizome and feeds on the content. This in effect leaves the rhizome as an empty shell. These worms can damage the water iris and need to be treated immediately. You’ll have to pick them off manually and drown them in a bucket full of water.