A winter cover of snow at Louisiana Iris Gardens, Tully, New York

by M. J. Urist

In the cold, short days of midwinter, the irises and I are enjoying the closest thing to real dormancy we get all year. While I lounge next to the woodstove sipping tea, reflecting on the past growing season and plotting next year’s gardening endeavors, the irises rest beneath a thick blanket of snow. The thirty and forty degree temperatures of late autumn and early winter, mild for our climate, would have been the harshest of conditions for their southern brethren. Even so, the robust fans of leaves, dutifully pared back to nubs in late summer, had managed to push out a foot or more of new growth before the snow fell. Often the first question I am asked is, “You can grow those up here?” Then will follow, “Aren’t they cold tender?” “You have to grow them in water, right?”



The first irises arrived in late September 2007. Seven irises were tenderly planted in meticulously-prepared beds. We had already experienced one killing frost and I was concerned this wasn’t going to go well. Then three weeks later with the first snow looming on the horizon, a carton of over 150 rhizomes to “experiment with” showed up on the Fed Ex truck. This necessitated an immediate sun up-to-sun down guerrilla planting operation performed with the assistance of one of my son’s friends. We turned over a swath of sod and weeds, pulled rocks and briars, amended the soil with peat, compost and aluminum sulfate, then planted and mulched the entire 400-square-foot bed. I crossed my fingers and started some concerted study of Louisiana Iris culture, discovering SLI along the way. As these things often go for gardeners lacking in common sense, what began as a dare to try a new plant has now grown into a nursery of over 150 cultivars and 5000 sq. feet of beds.

Sparse information was available for this endeavor when I started, and even less telling me what to expect about how they would behave in the drastically different conditions found in Central New York. My garden sits at about 1300 feet above sea level, a moderately high elevation for the hills about fifty miles south of Lake Ontario, in Zone 5B. What I do have is excellent soil; three feet of fertile teal-silt-loam left behind as the glaciers retreated, in a 100-year flood plain.

Kristin Nicholas, a louisiana irisKristin NicholasIn retrospect, perhaps it was better to undertake the growing with less information rather than more. Much of what I have read and heard along the way, even from those who know the plants best, would have been unduly discouraging. For example, I was told that only cultivars with a strong brevicaulis lineage would thrive up here. Elaborate methods of protecting the rhizomes from inclement weather were suggested, as well as generous irrigation (if not water culture) and pH requirements. As it turns out, pretty much every rhizome I’ve put in the ground has performed. Only a handful or two have failed to bloom regularly, and I’m willing to take responsibility for some of that failure as a result of poor placement. We’ll soon see if I’m correct, since last fall I moved every plant that hasn’t performed in its original location to sunnier ground. Last summer saw a number of plants show first bloom after three full years in location, among them both species I. nelsonii and I. brevicaulis. And some plants just seem to take longer to settle in.  Tetraploids generally seem to be reluctant bloomers, although Kentucky Cajun had shown nicely for the past two years. For the most part, once the plants are established, bloom is reliable and increase is vigorous.

Over the last six years, the degree of success I’ve experienced with the irises has left me with a much more relaxed approach to their culture and care. I’ve drafted guidelines that I send out with orders and dutifully share when I speak to garden and iris clubs. In reality, given some basic gardening know-how on the part of the grower, the irises grow themselves. My personal experience doesn’t extend to water culture, though I have recently begun seeding all my friends’ and neighbors’ ponds and ditches with rhizomes in the hope that I can learn something about how it works here. Beyond cautioning to plant above the high water line and allowing the irises to seek their own level in the water, I’ve had little to offer in the way of assistance.

The three most important requirements for Louisiana Iris culture are fertile soil, adequate moisture, and full sun.  I understand that Louisiana Irises grown in the south actually benefit from some shade, but where I am, absolute full sun is required for reliable bloom. With these needs met, the irises virtually leap out of the ground. There are differences in the yearly cycle. Growth slows to a crawl in winter, while in Louisiana the irises are putting out their pre-bloom growth and increase. When the irises are in full April bloom in Louisiana, the irises here are just shaking off the last of the snow and cold and sending up new tender leaves. Bloom comes in mid-June to early July, just between the Siberians and Japanese. I understand that Louisianas can and sometimes do go dormant during the late summer in the Deep South. Here, the irises put out lush growth all summer. Most years the rainfall is adequate for good growth. Only minimal supplemental water is helpful as the plants put up bloom stalks, or perhaps in the heat of July just to keep everyone happy. Strong growth continues right up until the very cold weather comes, usually late in November. I’m not sure how any of what I have learned translates to culture in the middling zones (6 and 7) to my south, but I’m pretty certain the success here is largely due to that white mulch that blankets the iris field for much of the winter. However, as with much of the country east of the Mississippi, last winter (2011-2012) was a very cold, dry, snowless season. It also coincided with my decision to leave an entire 100-foot row of irises unmulched as a test of the efficacy of snow only as protection. While my bearded irises virtually flung themselves out of the ground (along with a number of other cherished perennials), the Louisianas held tight.

A stalk of Lone Star entered in an iris showLone Star

It’s worth mentioning again that I am fortunate to garden in a very loamy soil. Gardens with predominately clay soil would benefit from bed preparation with plenty of organic material to improve soil structure. Despite the harsh conditions, the test irises performed at least as well as the rows that were tucked in tight. In fact, the 2012 bloom season, while arriving seven to ten days earlier than past years, was the most floriferous yet.

There are differences in the appearance of these Yankee irises. To anyone accustomed to viewing them in the South, these irises look stunted. Probably because they have only a short time, roughly six weeks, to transition from winter conditions to bloom, the stalks lack on average two to four inches in height, and one or two bloom positions. Thus far, any reliably performing registered iris has put out a minimum of three to four flowers. For the purpose of garden and bench judging, this begs adherence to the caveat that the growing conditions be considered. Even so, when I find a worthy-looking seedling, even though it may only put up a nice four-flower stalk, it’s packed up and shipped south for further evaluation.

Another variation you might notice is color saturation. Located between 42 and 43-north latitude, even at the summer solstice (which coincides with bloom), the sun’s intensity is much less than April in Louisiana. Consequently, the colors are much richer. Flowers are less subject to fading. Contrast in bi-colors and bi-tones is more pronounced. And finally, the rhizomes! Probably because the plants are growing in moderate temperatures with adequate rain all summer, fall dug rhizomes are robust.

We do have some different challenges with pests up here. Iris borers are, of course, the bane of northern iris growers, and this garden is no exception. As a Master Gardener, I am committed to employing the least noxious controls possible. Under any normal growing conditions in a home garden, iris borers can be adequately addressed through meticulous garden hygiene and close attention to plant health. I typically begin each morning with a walk through, coffee in hand, looking for the telltale signs of the vermin. I have come to embrace the wicked pleasure of diving into the growing tip, extracting the larva, and feeling it pop between my fingers as I dispatch it to some other plane of existence. I find early morning is the best time to make the interception before they can cause any real damage. If I’m too late, I’m not above uprooting a rhizome and going in after it on the spot. The difference I have found between borer damage in Louisianas vs. Bearded irises, though is that the Louisianas rarely develop rot or roll over and die from an assault. Even when I have dug up a rhizome in the fall only to find it completely truncated, they generally respond by throwing out a ridiculous amount of increase.

The other pest that will cause problems for Louisianas in the Northeast is the bud fly maggot or Neorthochaeta dissimilus. As with borers, garden hygiene and close inspection are the first lines of defense, but plantings are quickly overtaken and the result is devastating, though not fatal. If you are not familiar with bud fly, the larvae enter the flower buds to go after pollen, destroying all flower parts in the process. Close inspection will show a tiny pinprick hole, usually in the terminal bud. It is possible to remove the damaged bud, find the larva and destroy it, and enjoy the bloom on the remaining flowers. I have rarely found more that one larva on a stalk. If you miss the larva before it exits the first bud, it becomes a challenge to follow it down the stalk as it travels from bud to bud, increasing in size and damage potential as it goes. At any rate, the presence of bud fly larva on a plant essentially precludes using that bloom stalk for exhibition or hybridization. Out in the production beds, I confess that I am forced to employ chemical controls to deal with these pests. Systemic pesticides are applied under strictly followed directions with careful attention to the timing of application to minimize any impact on beneficial insects and pollinators. This is not something I feel good about, but it would be impossible to grow on this scale, otherwise.

blossom of Choctaw RidgeChoctaw Ridge
A generous application of fertilizer is just as important in the north as anywhere, though some adjustments need to be made to accommodate the growing cycle. I apply a balanced granular N-P-K after bloom, usually in late July. This seems to ensure vigorous growth through the summer and into fall, allowing them to develop a strong root system before the ground freezes. Springtime poses a challenge for fertilizer application. Because there are wide fluctuations in temperature between March and April, I hold off applying 5-20-20 until the weather stabilizes, usually in the last week in April or first week of May.

While almost all of the over 150 varieties planted out in the field have thrived and bloomed over the last six years, some have been outstanding performers and warrant mention. LONE STAR was the very first iris to bloom in my yard and has continued to be one of the most reliable plants in the garden. It was LONE STAR that won best in show at the Central NY beardless show last June. I always encourage northern gardeners to include this when they first start growing Louisianas because it is virtually foolproof in our area. DIXIE DEB is another iris that shines in the Northern garden. It always gets a lot of attention from visitors thanks to the brightly floriferous clump it forms. FLAREOUT has been another reliable bloom, coming late in the season. It also makes a bold statement, despite its smaller stature. If there is any drawback, it is its tendency to go dormant after bloom. Since this is not typical for Louisianas up here, the first time I saw it throwing off leaves, I panicked, thinking it had some horrible disease. It never fails to recover before fall, and it’s not uncommon to look across the garden as I prepare beds for winter, and see a handful of blooms again. With so many nice flowers blooming out there, it is hard to recognize just a few special irises. EDNA CLAUNCH has been an outstanding iris with a long bloom season and vigorous growth. Most visitors to the garden pick CHOCTAW RIDGE as their favorite red, and of course it is the iris I liked enough to put in my logo. KRISTIN NICHOLAS made a splash last year with a dense clump of flowers in luscious color. CAJUN SUNRISE never fails to draw a crowd, its normally vibrant color even more intense in the northern latitude. By far, though, the single most provocative bloom in the garden every year … the biggest attention getter, especially as it’s the first to bloom every year … the one everyone in my immediate circle of family and friends looks for and knows by name: BLACK WIDOW!

There has been increasing interest in growing Louisiana Iris amongst iris aficionados in my region, but I hope to see that interest spread to hobby gardeners looking for something different to try. Awareness of Louisiana Iris as a viable addition to the garden landscape in the Northeast is slowly increasing. I’ve added a mixed display bed to my own landscape to demonstrate the use of Louisiana iris in a succession of bloom. I’ve found a number of plants that thrive under similar growing conditions, including Echinacea, Digitalis, Hemerocallis, Lobelia, Aster, and Monarda species. Recently I’ve been in conversation with a local landscaper specializing in rain gardens. The ability of the Louisiana Iris to withstand some fluctuation in water level, as well as its tendency to retain good-looking foliage through the season makes it an appealing plant for this application. As we say, Louisiana Iris, truly a fantastic garden plant! … Even in the snowy north!