Disease problem? Or?

rosefollyJuly 10, 2008

I was doing the mid-summer pruning and cleanup of my front garden. When I got to my tall bearded irises, I patted myself on the back for their robust good health. They bloomed well this spring, have faultless, unmarked, healthy leaves, and are spreading vigorously. As I pulled off the withered old leaves I discovered that the roots of several were quite mushy. At first I thought it was just a case of too much mulch -- and that indeed may be the cause. I did see some holes in a couple of rhizomes near the stem, perhaps as large as a quarter. When I peeled off outer leaves the root under that was clean and whole. I observed pillbugs but no other kind of bug in the soil.

Is this likely to be just too much mulch keeping the roots too damp, or do I have a more serious problem? I dug up the plants that had mushy rhizomes and discarded them. Healthy looking rhizomes attached to them I also dug up and cleaned to dry, set in the shade (it's in the upper 90's here) and cut the leaves in a fan. I plan to replant them in a day or so. Several irises that looked healthy I left in place.

Please advise if I can replant in the same area or should move them to a new one. Also, do I need to soak the rescued rhizomes in a bleach solution before replanting? And ought I to remove the irises that looked okay to another spot?

Thanks for any advice.


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iris_gal(z9 CA)

I didn't answer because I'm not experienced with rot. Had it once with one iris.

Some people would say not to replant in the same area. I say look at the soil conditions in that area. Is the soil allowed to dry between soaks? Especially in warm temps. Are the tops of the rhizomes kept exposed to air and light? Are they getting too well fertilized with a high nitrogen fertilizer? (10-10-10 is too high --- first number needs to be lower)

When you said they are looking very healthy right now, I became suspicious. Mine look rather tired now. Maybe yours are rebloomers and their appearance is different at this time of year?

The 10:1 water:bleach dip won't hurt but not necessary if you've cut away all rot and allowed them to cure a couple of days. Only give one thorough soaking after planting and wait 1 month before the next soak. This is the rule my grower friend uses in her decomposed granite "soil" and I found it works in my improved adobe soil. Her average summer temps are 90-100 & mine are 80-90.

    Bookmark   July 13, 2008 at 1:21AM
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Iris Gal, thanks. I threw away the mushy ones, left three healthy ones but pulled the mulch off them. Three healthy ones that I dug up I will replant in another spot.

These are occasional rebloomers, but not reliable. I don't know the name but they are a deep, rich purple and the most robust irises I have ever grown, though admittedly I am not a very experienced iris person. I know what you mean about the faded foliage. My Batik irises look like that, as do my other (but different) unidentified purple irises.


    Bookmark   July 13, 2008 at 6:24PM
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