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CULT: rhizome size vs bloom vs soil conditions vs climate

Hello All,

I have noticed an odd phenomenon in my iris beds this year, and I'm still trying to figure out which of many factors are playing primary roles here.

With my very short growing season, it often takes bearded irises of all classes several years to settle in and start blooming regularly.

Several years ago, I created a new bed in iris-virgin soil (used to be hayfield) which I stupidly and severely overfertilized at the time of its conversion to irises. This "hayfield bed" is in full sun and in an open, unprotected area, fully vulnerable to all climatic conditions.

My primary iris beds (also stupidly overfertilized years ago and still trying to leach out the extra chemicals) are located over my septic drainfield in an area behind the house protected on one side by the house and on all other sides by a variety of taller trees, bushes, and shrubby undergrowth. These partially shaded beds have been growing irises for about 12 yrs.

Neither the hayfield nor the primary beds have been fertilized in years, and I have not provided any supplemental water to either of them at all this year. Both beds were initially amended with essentially the same things, and the primary beds have been dug and reamended a couple of times over the years. Both beds are planted on raised windrows to improve drainage and reduce rot. Both beds are fenced to reduce (but not necessarily eliminate) animal traffic.

This year is the second year in a row when difficult climatic conditions have had severe consequences in the iris beds, though the stressors each year have been somewhat different.

Now here are the interesting observations I've made this year. These comments, btw, refer primarily to dwarf and median beardeds. TBs aren't even worth mentioning in a difficult year like this one. In the fully exposed, hayfield bed, there was fairly minimal bloom this year. Many irises that started growing in early spring have since weakened, sickened, and in some cases, died - I assume as a result of the repeated climatic stresses to which they were subjected earlier in spring. There's been more of the enigmatic "scorch" in that bed this year than I have ever seen here - clumps losing all foliage while rzs remain firm and apparently healthy looking. What is even more puzzling, though, is the rz size of the surviving irises in that bed. They are HUGE! They look like those West Coast lunkers so many irisarians drool over. I have NEVER managed to grow rzs even a tenth that size here before. Is it the fact that that bed was virgin soil several years ago? Or is it the full sun position? I know it's not extra water, cuz it hasn't gotten any more than average rainfall this year.

Meanwhile, back in the old soil of the shadier, protected primary beds, bloom was much better on the MDBs and SDBs (poor bloom on most beardeds taller than SDBs), there is NO scorch, losses are minimal, and the rzs are tinier than I've ever seen them. I mean, raisin tiny. These beds are in serious need of digging and reamending, because they are overrun with grass and weeds of every description and haven't been dug in too many years. So, I'm not surprised by the rz sizes in those primary beds.

I guess what I'm finding so surprising is not only the massive rz sizes of the surviving irises in the exposed, hayfield bed, but also the amount of dead and/or dying (NOT rotting) irises in that same bed vs lack of same in the protected primary beds. It would seem that in my climate, at least MDBs and SDBs (with their reduced requirement for full sun) do better in a growing location where they receive some natural protection from the worst of the weather. Even the taller medians and talls are much healthier in the protected beds, though their bloom potential certainly suffers without full sun. And once again, in my experience here in the Northland, mature rz size seems to have nothing to do with either bloom or health of the plant.

Interesting year here.


Shadowood - http://lfrazer.com
The Irises of Shadowood - http://lfrazer.com/iris/
Wallplates With Panache - http://lfrazer.com/wallplates/

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