There is a growing trend in American gardening that promotes the planting of native plants.
In Louisiana, we have many wonderful trees, shrubs and herbaceous plants native to our state and the southeastern United States that are excellent choices for our landscapes, and I try to encourage their use whenever possible.
This time of year, one of my very favorite native plants is coming into bloom, and the blooms produced are among the most colorful and beautiful in the plant world.
I am talking about Louisiana irises.
Louisiana iris is the name used worldwide for a unique group of Louisiana native iris species and, in particular, their hybrids.
Their extraordinary beauty and reliability in the garden have made them increasingly popular, but they still deserve more recognition and use here in their home state.
Though a number of iris species are native to Louisiana, only five species -- Iris brevicaulis, Iris fulva, Iris giganticaerulea, Iris hexagona and Iris nelsonii -- are known as Louisiana irises.
Although I. brevicaulis and I. fulva are native to the Mississippi valley from Louisiana to Ohio, and I. giganticaerulea and I. hexagona are found along the Gulf Coast from Mississippi to Texas, only in south Louisiana do all five species occur together. There were once vast native stands of these irises, particularly in the area now covered by New Orleans.
These five iris species will interbreed with each other but with no other species. The crossing, or interbreeding, of these species has resulted in the modern hybrid cultivars we grow today.
Their large, attractive flowers cover a broad range of colors including many shades of blue, purple, red, yellow, pink, gold, brown, lavender, burgundy and white.
Cultivars with bicolor flowers of contrasting colors, bright yellow signal markings or ruffled petals add to their beauty.
When to plant
The best time to plant Louisiana irises is in August and September, when they are dormant, but you can buy and plant them now while they are in bloom and pick out colors and types of flowers you like best.
When purchased and planted now, however, Louisiana irises need to be handled carefully to avoid damaging the foliage and flower buds.
Although in their native habitats the original species often grow in swamp or bog conditions, and Louisiana irises make outstanding additions to aquatic gardens, they can also be grown in ordinary garden beds with excellent results.
Their culture is really quite easy, as long as you provide the right growing conditions and are familiar with their seasons of growth and dormancy.
Louisiana irises should be grown with as much direct sun as possible. Although they will tolerate shade for part of the day, at least about six hours of direct sun are needed for good blooming. Avoid locating beds near large evergreen trees that create shade and extensive root systems that would compete with the irises.
When preparing a spot to plant Louisiana irises, incorporate a generous 3-inch layer of compost, rotted manure or peat moss and a general-purpose fertilizer, following label directions.
The irises prefer a soil high in fertility and organic matter. They also generally prefer an acid soil, though here in New Orleans where our soils are slightly alkaline they do very well.
Aquatic culture is one of the easiest and most natural ways to grow these irises, and the foliage tends to stay more attractive in the summer.
Simply place your potted iris into your decorative pond or aquatic garden so that the rim of the pot is a few inches below the water's surface.
Every one to two years, divide and repot them in heavy garden soil. You can also simply plant them into the soil at the edge of a pond, and they will grow along the edge and down into the shallow water.
In flower beds, plant Louisiana irises at the same level they were growing in the container. The rhizome should be at the soil surface.
Care must be taken to protect the foliage and flower stalks when planting irises from a container this time of year. They might be top-heavy and unstable when first planted, but do not allow the foliage or bloom spikes to flop over or break.
If necessary, place a stake next to the plant and loosely tie it up. Established plants generally do not need to be staked.
The farther apart the irises are planted, the longer they may be left without dividing. If the plants become too crowded, they will not bloom as well. Crowding and insufficient sun are common reasons for poor bloom.
If you are planting several plants in a bed, plant them in a group spacing them about 12 inches apart.
Tending to iris
Providing adequate moisture is an important part of growing Louisiana irises. Keep newly planted irises well-watered, and continue to water during dry weather until late June.
After that, as the irises go dormant, watering is less important, unless you're trying to keep the foliage in good shape. Resume watering as needed in late September as the plants come out of dormancy.
Fertilize your irises in October and February. Irises growing in containers in aquatic gardens should be fertilized by lifting the pot out of the water and placing aquatic fertilizer tablets below the soil surface.
Always keep irises growing in beds mulched. This is an essential part of good culture, especially in the summer. A 2- to 3-inch layer of leaves, pine straw or other mulching materials helps prevent sunscald of the rhizomes, along with reducing weeds and maintaining soil moisture.
Louisiana irises generally set seed pods after flowering. These seed pods grow to be large and heavy, and if left on the plant will tend to make them lean over and look less attractive. Also, the production of seeds uses up a lot of food and energy that could be better put to use by the plant.
So, to prevent seed pod formation, the flower spike should be removed back to the point where it emerges from the foliage as soon as all of the flowers have bloomed.
If you have never grown Louisiana irises, you will be pleased with their easy care and beautiful flowers. If you already have some, consider adding some new colors to your collection.
LOUISIANA IRIS RAINBOW FESTIVAL: Celebrate our state wildflower at the Louisiana Iris Rainbow Festival in the New Orleans Museum of Art's Sydney and Walda Besthoff Sculpture Garden in City Park, April 2, 11 a.m. to 4 p.m. A great idea is to see the Spring Garden Show and then walk across the street to the Sculpture Garden to see the irises that now line the lagoon, and listen to a couple of talks on Louisiana irises.
LOUISIANA IRIS DAY: Longue Vue House and Gardens will be showing off its extensive collection of Louisiana irises April 9, noon to 4 p.m.; free. The irises were planted in 1950s by Caroline Dormon, an early conservationist, educator and advocate for native plants. For information, contact Hilairie Schackai at 504.293.4726 or email@example.com.
I am adding a large amount of oak leaves to my compost bins. Will I end up having too much alkaline, and, if so, will I need to add more nitrogen to balance it out?
Finished compost, almost regardless of what is used, generally ends up about neutral in pH. However, you may want to add a little nitrogen-containing fertilizer as you build up your pile to enhance the decomposition process. The fungi and bacteria will decompose the low-nitrogen oak leaves more rapidly if they are provided with some nitrogen. The nitrogen has nothing to do with pH, though.
I need to move my large adult azaleas from the front of my yard to the back of my yard. They are about to bloom, so how long after they finish blooming can I safely dig them up and transplant them? Also, should I do anything to them to help them start growing and thriving in their new location once I transplant them? Thanks for your help.
Jo Ann Rosenfeld
The best time to transplant azaleas is during the winter when they are dormant, from mid-December to mid-February. By the time they finish blooming, they will be in active growth, the weather will be getting hot and they will not tolerate the damage to their roots as well. Azaleas, like most plants, get the water they need from their roots. When they are dug up, the roots are damaged, and the plant's ability to absorb water is reduced. If you do this when they are dormant, they tolerate the damage better and are more likely to survive the move. If you do this when they are in active growth, they are less tolerant of the root damage and less likely to survive. The most important aspect of care once you have replanted them is to pay attention to watering. Given that the roots are damaged, water needs to be available to the remaining functioning roots at all times. Make sure plants stay properly watered during the summer. Keep in mind, however, that the goal is not to keep the soil constantly soggy, or you risk drowning the remaining roots.
We purchased a Louisiana sweet orange tree in a 10-gallon container last week and planted it. It is blooming nicely and starting to produce tiny fruit. The grower's website listed information on caring for it, including pinching off the fruit the first year when they get to pea size. We are reluctant to sacrifice what could be a plentiful crop of oranges but want to do what's best for the tree. What is your opinion on this?
The young citrus tree can only make so much food to support all of its various parts and enable them to grow and be healthy. It is important for a young tree to devote this food and energy to producing new roots, stems and leaves to get established in its new location. Ripening a crop of food would take a tremendous amount of the young tree's limited resources. So, the fruit is removed so that the tree can devote all of its resources to growing strong and thriving its first year in the ground. This is best for the tree. Commercial citrus growers strip the fruit from young trees knowing that the result will be a stronger, more productive tree in the long run. And, it is entirely likely the tree will drop the crop anyway. Indeed, production in young citrus trees is erratic the first three to five years after planting. It is possible the tree will not produce any fruit for the first few years while it is settling in. This is normal, so don't be too disappointed.
Dan Gill is extension horticulturist with the LSU Ag Center.
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