Why do rhizomes need sun?

veryzerJuly 31, 2012

It just seems strange given that a fan has many, many times the surface area. Just curious.

Thank you for reporting this comment. Undo
hosenemesis(SoCal Sunset 19 USDA 8b)

They don't need sun. As a matter of fact, I just learned that many growers plant the rhizome entirely under the soil, especially in very hot areas, so that the plant does not get burned.

The reason people tell you to plant your iris with the top of the rhizome exposed is because irises need good drainage or they can get bacterial rot. Rick Tasco at Superstition Iris Gardens says they plant their rhizomes just beneath the soil. He notes that rot is from injuries breaking the skin of the rhizome through which bacteria can enter. If there are moist conditions the bacteria are more numerous and can move about more easily to infect the plant.

Tasco recommends experimenting in your climate/soil conditions to find out what works best for you. I'm going to start planting 1/2 beneath the soil and 1/2 with the top of the rhizome exposed to see what develops here in So Cal.

If you let a lot of leaf litter and decomposing mulch sit on top of the iris you may be creating fertile conditions for bacterial rot as well, that that's something to be aware of.

Renee

    Bookmark   July 31, 2012 at 10:46PM
Thank you for reporting this comment. Undo
hosenemesis(SoCal Sunset 19 USDA 8b)

It was Chuck Chapman who gave that info. Here's a link to the discussion on Iris Lovers on Facebook.

Here is a link that might be useful: Iris Lovers Suzy Schneider post

    Bookmark   July 31, 2012 at 11:56PM
Thank you for reporting this comment. Undo
aseedisapromise

Thanks for the link. I've switched from planting mine half out/half in the soil, to planting one inch deep, and I always leave the roots on. It's convenient that there isn't such a big problem with nematodes here, so that the fact that we need the roots to keep the rhizomes from blowing away in the winter isn't a problem. We can have wet years, and dry years, and some parts of the city have clay soil, and some sandy, so a middle of the road course is best here. The soil changes from one side of my property to the other. It's sandier towards the creek, and gets more clay in it as you go upland. The rhizomes tend to migrate up to a half in/half out position for most of the iris. I've never done the bleach soak that all the folks on the Facebook group were adamant about, and haven't had any new iris rot, but I have had the dirt blow away out from under them, and they end up dried and shriveled and frozen. So, if it is an open winter, I need to mulch with branches or something to keep the soil in place. If it snows a lot, I need to get out as it is melting and clean all the debris away from them. Talk about frozen fingers. It is during those years that the bleach soak would be good insurance. Since I don't know which winter weather I'm going to get, I may take it up as a practice.

I have a lot of respect for the folks planting 10K rhizomes at a time.

    Bookmark   August 1, 2012 at 8:47AM
Thank you for reporting this comment. Undo
veryzer

Thanks, that makes much more sense.

    Bookmark   August 1, 2012 at 3:45PM
Thank you for reporting this comment. Undo
hosenemesis(SoCal Sunset 19 USDA 8b)

I have never soaked mine in 10% bleach water before either, but I'll bet I would not have gotten leaf spot here if I had. I will from now on.
Barb, I can't imagine your winters!
Renee

    Bookmark   August 1, 2012 at 8:47PM
Thank you for reporting this comment. Undo
aseedisapromise

I don't know, Renee. To get a disease you need a pathogen, a host plant, and the right conditions for the pathogen to grow. I wondering if the weather was just stacked against you. Was it mostly new iris that got the spots, or is it just in certain places in your garden, or is it sort of all over the place? If it was generally all over, it might be good to note if there are iris that don't have it. Well, the culture would have to be the same, I guess. Maybe the more crowded iris might be more susceptible. But knowing if some iris are resistant would a good thing. Setbacks are disheartening. Can you try some fungicide next spring?

    Bookmark   August 1, 2012 at 10:37PM
Thank you for reporting this comment. Undo
hosenemesis(SoCal Sunset 19 USDA 8b)

It has been much cooler and moister here than usual for the past three summers. I used Daconil this year in early spring and again at the end of the bloom season.

I think I introduced it with some nursery irises last year. It only affected the irises in one area of the garden. This year I divided almost everything, and I have been extremely diligent about removing affected leaves and about pulling off every old leaf, even before they get brown. I am hopeful that I have eradicated it and will no longer have to spray.

I have been told that Beverly Sills and other light pink irises seem to be more susceptible to it. I cut off all of the foliage of Beverly, sprayed, and moved the rhizomes to the back 40, and they were spot free this year. Keeping my fingers crossed!
Renee

    Bookmark   August 3, 2012 at 2:57AM
Thank you for reporting this comment. Undo
aseedisapromise

Sounds like you have the bases covered. I hope the weather is more amenable next year, and that all your work pays off with clean, lovely iris!

    Bookmark   August 4, 2012 at 10:05AM
Thank you for reporting this comment. Undo
texasredhead(z8Texas)

Have always wondered when it is appropriate to cut back the foliage on iris. My bed bloomed beautifully last year but hardly at all this year.

    Bookmark   August 9, 2012 at 9:02AM
Thank you for reporting this comment. Undo
aseedisapromise

I will answer, but really you should have started a new thread for this. You will get more responses that way.

Maybe your iris are getting crowded and it is time to dig them and throw out the old mother rhizomes and replant the new ones. When iris get crowded they don't bloom as much.

If you have reblooming iris, I don't think I would cut them back now. I don't have any that rebloom, but I still don't cut them back at all until it is going to have a heavy frost here, or sometimes I leave them all winter and then clean them up during a thaw in February. Some people cut them back at the end of summer or if they are looking nasty, which yours might be since it has been so hot this summer. I think it is up to you.

    Bookmark   August 9, 2012 at 3:04PM
Thank you for reporting this comment. Undo
texasredhead(z8Texas)

Thanks, and yes I know better.

    Bookmark   August 10, 2012 at 8:54AM
Sign Up to comment
More Discussions
Anyone know how to reach Zebra Gardens?
Hello! I found Zebra Gardens and their breathtaking...
redwolfdoc_z5
Bottle Rocket
Pretty Tall Bearded from last years bloom, Crossed...
criris_z8
Looking for iris Frost and Flame
Hi, I m looking for the iris Frost and Flame by the...
gibsongirl74_gw
Consequences of transplanting in winter/early spring, zone 5
Hello, I have a question about transplanting irises....
kmburton
Herbicide recommendation for iris bed
Hello, I am usually solely a contributor in the vegetable...
hokiehorticulture
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™