Techniques and methods of a successful pond planting
In the September SLI Newsletter; Walter Moores stated that the most important point to remember in the culture of any plant is to simulate as closely as possible the native habitat of the species. He certainly hit the nail on the head with that statement.
Growing Louisiana irises the natural way involves much less maintenance work, results in superior plant performance, and, of course, adds a beautiful new dimension to the garden.
I grew up in the South Louisiana countryside and always loved the natural world. I dug up irises in the wild (mostly I.fulva) to transplant into the bayou. After I finally ended up with my own place I began to collect wild irises again, and one thing led to another. Now I have most of my irises in water - except for the I brevicaulis, which do just as well in raised beds. I'm involved with many different aspects of gardening and consider Louisiana irises among the easiest plants to grow and just about the most useful garden perennial.
Construction of the beds is probably the most important aspect of water culture, and involves many hours of hard work. First, the soil must consist of a heavy clay or, as in my case, a fine silt with a very tight subsoil or hardpan. There is virtually no water loss due to seepage in my situation. I suppose if one weren't lucky enough to have this sort of situation, they could install a liner and place soil over it, but it makes me shudder to think of the labor involved. In my opinion, there is no comparison between water plants grown in the soil and those grown in containers. All effort should be made to grow water plants in soil as long as the growth rate is not too rampant. If seepage is a problem, the creation of a damp bog may be a more favorable option.
Next, an apparatus to control the water level is very important. I've constructed a small levee with a concrete spillway above. A four-inch PVC pipe with a screw-on plug allows me to lower the level of the pond by about 10 inches. In nature, the swamps dry up during the August-through-October period. Many beneficial things happen during this time, including aeration of the soil, seed germination and, in irises, dormancy followed by fall increase. There are many advantages to this practice of exposing the iris beds in fall. For one thing, it is infinitely easier to work in a dry soil than it is to slosh around in the mud. New beds can be prepared and established beds rejuvenated, and elevated paths can be constructed. But most important of all, this drying seems to stimulate increase much more than if the rhizomes remain under water all year. In addition to bed rejuvenation, this results in full clumps of healthy irises.
Full sunlight is definitely best for Louisiana irises, but most of us just must have some trees. If some shade is desired, it is imperative that it be from deciduous trees, which enables much sun during the period of explosive growth during late Winter and Spring. Bald cypress is a wonderful companion tree, but I've often wondered how Louisiana irises would grow under Black Gum, which turns scarlet and sheds its leaves as early as September. Anyway, the more sunlight the irises get, the better.
As for preparing the soil, with water culture you just can't fertilize the irises too much. When I first prepare a bed for Louisiana irises, I loosen the clay with a jackfork then cover the area with several inches of rotted horse manure and rice hulls. I then cover the area with the cheapest 8-8-8 I can find. Don't be wary, I've dug up rhizomes that were resting directly on a big chunk of fertilizer with no adverse effect. After spreading the material, I turn the soil over once. All I really want to do is place soil over the manure and fertilizer to hold it in place, which I feel reduces leaching into the water. This massive application of fertilizer at planting time is the only application I give them for the entire year. A two-year bed will only be top-dressed, but a three-year bed should be dug up, thinned out and prepared as above.
I don't have any advice regarding the effects of soil pH. My soil is around pH 6.3, but I have a feeling that heavy application of manure and acid fertilizer would stimulate good growth in alkaline soil.
Now for planting. Remember, this is water culture, so throw the usual rules out the window. The beds are dry soil in early Fall, but sooner or later they will be several inches under water. (I let runoff from drainage ditches fill my pond when all planting is completed.) Several critical factors come into play. If the weather remains dry, then much effort is required in keeping newly-planted rhizomes damp. Yet when the rains do come, every rhizome must have leaves out of the water. If the leaves are entirely submerged, pull the plant up as soon as possible and set it in a container until it gets tall enough so that at least three inches of leaf protrudes above the water. Very few irises will grow leaves up out of the water if their foliage is completely submerged when they are first planted
I'm now in the habit of placing new rhizomes in No. 1 containers, setting them in a wading pool until vigorous new growth of the required height allows me to just go push them into the mud later in the Fall. If a fan should rot, find the rhizome and cut off the rotten area. Rub Comet cleanser on the wound and place in a container in a shady, damp spot (preferably in a greenhouse) and be patient. They'll usually sprout new growth by Spring.
When changing out the varieties in a bed, allow the reworked new bed to remain fallow a couple of months. Remaining rhizome remnants will sprout, and can be removed to prevent contamination of the new bed.
Okay, all the hard work of planting season is over and winter approaches. Gradually the tropical water plants retire to their winter's sleep and the shrubs shed their leaves. But the Louisiana irises really begin to stand out. It's amazing how much growth they can put on during a mild spell in winter. The water also may help them survive severe winters. In the horrible freeze of 1989, I had some leaf-tip scorch but no rhizome damage, despite four consecutive days of deep-freeze, with lows of 14F, 9F, 8F and 18F! Down here in South Louisiana, winter always seems to end about the second or third week of February. This is when the irises really explode, and almost seem to change from day to day. It's amazing, but many times I've seen a little fingernail-sized rhizome grows enough during this season to produce a fine show stalk by April. There's really not much to do during this season but enjoy the plants and just check around for the first stalk to pop up on LAVENDER RUFFLES, GRACE SCOTT, or BELLEVUE'S NATIVE CHARMER. This begins around mid-March and increases exponentially until bloom peak, which occurs in my area around the first week of April.I've seen as many as nine stalks produced from one piece of rhizome planted during the previous Fall.
Eventually the bloom season winds down and my iris patch looks like a parade, with the best participants waving their little orange flags from recent hybridizing. It doesn't take long before it's back to work again. Every unwanted stalk must be cut and hauled off, otherwise rogue seedlings will contaminate the beds. At this time I find many advantages to water culture. For one thing, if you bend the stalks down so that the seed pods remain in the water there is absolutely no damage from Verbena Bud Moth. However, I have found a few huge cutworms that somehow manage to devour entire pods. I have never had rust on plants growing in the water, and no damage due to rabbits or armadillos.
The sweltering summer begins and a new task arises. Weeds are not a big problem with water culture, but can be if care is not taken to suppress them before they set seed. Needlegrass, pickerel weed and alligator weed can spread like fire if not controlled early. Until this year I controlled weeds by hand-pulling, but I'm shifting to a new strategy. If water hyacinths are allowed to invade iris beds, they suppress most of the weed growth but don't seem to bother the irises. They're also very pretty. What's more, when the beds dry up, the dead hyacinths prevent rhizome sunscald, so why not kill two birds with one stone?
A couple of summer chores remain. Around late June, seed pods should be ready for harvest. You don't want to wait too long, because the seed pods will turn to mush if they're hanging in the water and aren't picked early. Most pods remain intact, but who wants to lose that special cross? I plant my seeds in pots of plain dirt and control grass and weeks with Roundup until germination takes place in the fall. Another little extra midsummer job is "dormant rhizome rescue." On the slowpokes like CLARA GOULA, or with skimpy new plantings, I find the dormant rhizomes by feeling for them in the mud (just don't even think about the critters down there). I cut them from the new rhizomes at the point of juncture and yank them out. Treat them as above for rescuing rotten rhizomes. Be patient. This past season I had a BLACK WIDOW rhizome that remained dormant for nine months, then it sprouted five new plants.
It's difficult to make hard-and-fast statements about water depth. I've seen irises in one inch of water tend to grow towards deeper water, and those deeper than six inches want to crawl out. I guess it depends on the variety. A wildcat like PEGALETIA seems to grow just as rampantly in water one foot deep.
Well, this describes the way I grow most of my irises. I consider water culture of Louisiana irises a tremendous asset to the garden, especially when grown with tropical water plants and water-loving shrubs. I may have an "awe shucks" attitude and my methods may be coarse, but I've been very successful at stopping traffic, and haven't done too poorly at the annual show, either.
*Gordon Rabalais, of Arnaudville, Louisiana, is a member of the Board of Directors of the Society for Louisiana Irises. He grows Louisiana Irises, Camellias, Viburnums and even grapes in his large garden near the banks of the Vermilion River, The focal point of the garden is the pond planted with Louisiana irises.
Editor's Note: This article first appeared in the SLI Newsletter in the Summer 1992 edition.