Irises forum: Rhizomes do NOT need exposure to air and sun?

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caitlinsgarden
Jul 2, 2014 6:16 AM CST
This was just said in a FB iris lovers group. Any comments?
Name: Arlyn
Whiteside County, Illinois (Zone 5a)
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crowrita1
Jul 2, 2014 6:27 AM CST
Yup, I'd agree with that statement....Arlyn
Name: Bonnie Sojourner
Harris Brake Lake, Arkansas (Zone 7a)
Magnolia zone
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grannysgarden
Jul 2, 2014 6:46 AM CST
Depends on whether you mean entire rhizome uprooted from soil or like we say here in my zone, plant them like you imagine a 'duck on water' their little backs and neck out of the water and their little bellies and feet in the water. In other words we plant the rhizome where you can see the top of it above the soil. But when taking irises out of the soil I never place them in the sun and the sooner they can get back into the soil the better. If I find a rhizome that has some decay on it I do one of two things depending on the amount of decay. I either leave it in place and use a spoon to scoop out all the decay and then sprinkle that area with comet and leave it exposed to heal or callous if possible, or, I take it up, cut off the decay and let it set out in the shade and dry overnight to allow the wound to callous over and then replant. I never put an iris back into the same soil where it had problems nor do I compost any iris that has problems.
I love my garden.... and Jesus, and coffee, and naps.......
Name: Tom
Southern Wisconsin (Zone 5b)
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tveguy3
Jul 2, 2014 7:18 AM CST
Barry Blyth says that he covers the rhizomes in the area where he lives. The hot sun is to hard on them. I have sent iris to friends in Arizona, and told them to cover them with mulch for the same reason, and they have had a good bloom season this spring. That wouldn't work here though.
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Name: Bonnie Sojourner
Harris Brake Lake, Arkansas (Zone 7a)
Magnolia zone
Region: United States of America Region: Arkansas Master Gardener: Arkansas Irises Bulbs Seed Starter
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grannysgarden
Jul 2, 2014 7:54 AM CST
If the summers here keep getting hotter I may have to resort to covering them. I now plant where they do not get sun from dawn to dusk but where the afternoon rays are blocked. I have friends who mulch over winter but that seems to make more problems in the spring rains than anything else here. I remove all leaves and iris debris and just let them go through the winter on their own. So far, so good. I did worry this last winter as some I had put in pots. I would go out to check when the weather permitted and the entire pot was a ball of ice. I had to break it off with a rock. I guess they like being covered in ice better than baking in the sun.
I love my garden.... and Jesus, and coffee, and naps.......
Name: Debra
Garland, TX (NE Dallas suburb) (Zone 8a)
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lovemyhouse
Jul 2, 2014 9:03 AM CST
Mine are covered because of our heat and drought conditions. They may not have as plentiful a bloom, I dunno. (Maybe I should experiment.) They seem to do fine otherwise.
If you don't ask, the answer is always 'no.'
Name: Leslie
Durham, NC (Zone 8a)
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Lestv
Jul 2, 2014 9:04 AM CST
I have read that you can cover rhizomes with about an inch of soil in hot climates, and wondered if I should do that here in NC. BUT: I had a old clump of Acoma that were buried in soil under a tree in my back yard. They would bloom only sporadically, but once I pulled them up and planted them on top they took off like gangbusters. There was even a yellow noid buried that I never even knew was there! It is quite pretty and ruffly, but sure didn't grow before it was released from it's soil covering.
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South central PA (Zone 6a)
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DaveinPA
Jul 2, 2014 10:19 AM CST
From all I have read the top of the rhizome should be exposed to the air and sun when in an environment that tends to get/stay wet. That helps it stay drier and prevent rot of various sorts. In the hot, dry, sunny locations a light covering is good to protect it from over drying.
Name: Kent Pfeiffer
Southeast Nebraska (Zone 5b)
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KentPfeiffer
Jul 2, 2014 7:09 PM CST

Moderator

That's a bit of a myth, or maybe oversimplification would be a better term. There's nothing in the physiology of an iris rhizome that would indicate that it needs exposure to air or sunlight. It has no chlorophyll, for example. The rhizome is essentially just an energy storage organ.

I suspect the idea that the rhizome should be partly exposed above ground was originally promoted by commercial growers as a simple and effective means of preventing some of their customers from burying the rhizomes as if they were tulip bulbs, which would clearly cause problems because it puts a significant portion of the leaves below the soil line and leaves obviously aren't adapted to that. Just a guess, though.

And, of course, irises generally grow just fine with the rhizome partially exposed, so there's little harm.

Many funny ideas get passed around like that. When I was a kid, my Mom and grandma always cut their iris leaves back to six inches or so in early July, and so did everyone else we knew. Why? Because the orders from Schreiner's arrived in July with the leaves cut back. Shrug!
Name: Mary Ann
Kentucky
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Muddymitts
Jul 2, 2014 7:31 PM CST
Omigosh Kent -- what a great story! And a perfect example of how traditions get established.

But!!! I wonder if their efforts in that regard didn't maybe discourage borers?? Just a thought...............................................

I just realized what a wonderful exposure you had to Irises as a boy. Your Mom and your Grandma ordered from Schreiner's? Wow.
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Name: Kent Pfeiffer
Southeast Nebraska (Zone 5b)
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KentPfeiffer
Jul 2, 2014 8:13 PM CST

Moderator

I'm actually not sure if my Mom or grandmother ever bought irises from Schreiner's, but at least some of the more serious irisarians in the area did. I remember the catalogs in the spring and the boxes of rhizomes in the summer, but I don't think they were Mom's or Grandma's. It would have been out of character for them to spend very much money on flowers. Smiling Mom was born in 1941 so you can imagine the influence the Depression/Dust Bowl had on her parents' thinking, and her too to some extent. They did love to grow irises, though.

The Schreiner family has been selling irises a long time, at least since the 1930's (maybe a decade or two before that?). I'm a bit embarrassed to admit that I didn't know there were OTHER commercial iris growers until about a decade ago.

Name: Paul Anguiano
Richland, WA (Zone 7a)
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psa
Jul 2, 2014 8:19 PM CST
We're very hot and dry here, with sand/silt soil. I've noticed my beardeds like to have their rhizomes a bit deeper here than I've planted them elsewhere. The sun does seem to be hard on them.
springfield MO area (Zone 6a)
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Frillylily
Jul 2, 2014 8:31 PM CST
If I cover mine with dirt they rot. promptly.
Name: Bonnie Sojourner
Harris Brake Lake, Arkansas (Zone 7a)
Magnolia zone
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grannysgarden
Jul 2, 2014 9:32 PM CST
Mine too. Also, no bloom at all. Even if I use mulch it keeps moisture around them and they have spots and rot. Perhaps if I used sand or perhaps if it was not so humid here most of the time it would work.
I love my garden.... and Jesus, and coffee, and naps.......
Name: Kent Pfeiffer
Southeast Nebraska (Zone 5b)
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KentPfeiffer
Jul 2, 2014 11:08 PM CST

Moderator

I'm sure that's true, but it's not because the rhizome inherently "needs exposure to air and sun". It's a result of the soil type you garden in, soil moisture, atmospheric humidity, temperature, and likely a number of factors we are unaware of, all combining to promote the growth of the pathogens that cause rot. Getting the rhizomes up out of ground, in your situation, changes enough of those factors to reduce the virulence of the rot causing pathogens.

Rather than say that, people say 'iris rhizomes need to bathe in the sun'. It's easy to understand why they say that Hilarious! , but it isn't strictly accurate. Smiling
[Last edited by KentPfeiffer - Jul 3, 2014 10:28 AM (+)]
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Orchid40
Jul 3, 2014 3:10 AM CST
Here in Victoria, Australia we have some fiercely hot Summer and cold wet Winters. I tend to keep the rhizomes as uncovered as possible during the wet months to minimise rot. Even so, I still lose a few. In Midsummer I let a light covering of soil cover them to avoid them being scorched. I live fairly close to Barry Blyth's farm, and their rhizomes are very near the surface. I believe that it just depends on the local climate whether you cover them or not. That's just my opinion rhough.
Name: Leslie
Durham, NC (Zone 8a)
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Lestv
Jul 3, 2014 7:44 AM CST
Interesting to hear that your mom cut the fans in July, Kent. My dad always does that too, but not because of anyone getting cut fan iris. He grew up in Illinois and lives in Michigan, and must have learned it somewhere along the way. It wasn't until much more recently that he started ordering iris. I will need to ask him why he cuts them down so early. I told him to leave them this year.
My road calls me, lures me west, east, south & north; most roads lead men homewards, my road leads me forth. - John Masefield
Name: Ken
Traverse City, Michigan (Zone 5a)
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bramedog
Jul 3, 2014 9:27 AM CST
Leslie, he may cut the leaves down here in Michigan because we get high humidity thru the summer months and the leaves get those oblong fungus spots on them. I am starting to trim them down and spraying a fungicide on them now.
Name: Bonnie Sojourner
Harris Brake Lake, Arkansas (Zone 7a)
Magnolia zone
Region: United States of America Region: Arkansas Master Gardener: Arkansas Irises Bulbs Seed Starter
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grannysgarden
Jul 3, 2014 11:02 AM CST
I have friends that cut them back due to the tips browning due to lack of rain. They insist that brown iris tips make their gardens look tacky. To each his own I guess. I try to keep mine watered the first sign of a tiny brown tip. lol
I love my garden.... and Jesus, and coffee, and naps.......
Name: Arlyn
Whiteside County, Illinois (Zone 5a)
Irises Beekeeper Region: Illinois Celebrating Gardening: 2015
crowrita1
Jul 3, 2014 11:39 AM CST
And in spite of all our "care", the iris still manage to do alright! Rolling on the floor laughing We all need to remember that what works well( or at least has no adverse affects!) in MY garden, in Illinois, may be "sudden death" to plants in Maine, California, or where ever ! Weather is different, soil is different, and there may be a big difference in culture, as well. So, while what we hear about on the forums can add to our knowledge, we still need to consider our OWN local conditions! In the extremely sandy soil I have, I usually plant with about 1" of soil covering the rhizome, while in the "amended" beds, I opt for surface planting. I don't cut the fans till fall clean-up time, figuring that even a leaf with leaf spot, and a brown tip ,is better than no leaf at all.I irrigate the beds when the soil is dry to a depth of 4"-5", if it hasn't rained(NOT a problem ,so far THIS year!), that means I'm watering every other day in the 'sandy" beds, and every 4 days in the amended beds. We all may grow the same plant, but due to our local conditions, and the amount of time we can devote to it, we do it a little differently!....arlyn

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