Irises forum: Can I cut back the foliage?

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Name: Geof
NW Wisconsin (Zone 4b)
Region: Wisconsin Dahlias Garden Ideas: Level 1 Celebrating Gardening: 2015
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mandolls
Jul 22, 2014 9:42 AM CST
I know this is a really basic question, and I did try to search for it using the "search"

I have a lot of old fashioned noid yellow iris, They were here when I bought my house, planted in an area to shady for them to bloom. I have moved and divided them several times over the past 10 years, and they are beautiful until mid-late July.

The foliage then starts yellowing and dying back, and generally looks terrible. It takes a lot of time to cut leaves back individually as they get ugly. At this point in the season can I just cut them all back to 3-4" tall? Have they had enough time to store up nutrients for the winter?

Thanks for the help
South central PA (Zone 6a)
Irises Region: Pennsylvania
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DaveinPA
Jul 22, 2014 10:18 AM CST
Based on all of my known science and lore there are two times for cutting foliage: when it looks bad and browns, for aesthetic reasons, and also in the early/late fall if desired for same reason.
Story is that Schreiner's in their early days cut foliage for shipping and it spread to others thinking it had to be cut in July/August, but it does not. Just getting out "spent" foliage is usually sufficient.
Name: Tom
Southern Wisconsin (Zone 5b)
Irises Vegetable Grower Butterflies Region: Wisconsin Keeps Horses Cat Lover
Dog Lover Keeper of Poultry Daylilies Celebrating Gardening: 2015
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tveguy3
Jul 22, 2014 10:40 AM CST
A lot of people do cut it back in the late fall though, and it doesn't seem to hurt anything. Some burn it off in the spring, if they are away from things and fire won't hurt anything else. The main reason for getting rid of the old leaves in the spring is to help reduce the iris borer population. In the other seasons getting rid of the dead leaves helps reduce the moisture around the rhizomes to help reduce the problems with rot. One of my friends cuts it back every fall, and I usually don't. We both have good results.
I am not afraid of an army of lions led by a sheep; I am afraid of an army of sheep led by a lion. - Alexander the Great
Name: Lucy
Hamilton, MA (Zone 6b)
irises
Charter ATP Member Cottage Gardener Enjoys or suffers cold winters Region: United Kingdom Region: Northeast US Irises
Region: United States of America
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irisarian
Jul 22, 2014 2:11 PM CST
We cut back Siberian foliage in the fall & just trim the bearded irises which are brown. The foliage helps the plants make food for the following year.
South central PA (Zone 6a)
Irises Region: Pennsylvania
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DaveinPA
Jul 22, 2014 4:51 PM CST
Instead of cutting back the foliage in the fall I just make sure the fallen leaves don't pile up on the clumps which can allow overwintering of undesirable critters and of course remove the foliage that has died off for the same reason. Even doing this I do get the occasional undesirable borer. The back end of one is shown here.

Thumb of 2014-07-22/DaveinPA/3d70f2

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
Gardens in Buckets Garden Art Plant and/or Seed Trader Moon Gardener Garden Ideas: Master Level Celebrating Gardening: 2015
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grannysgarden
Jul 22, 2014 5:12 PM CST
How do you find borers in an iris rhizome? Do you have to cut it open or can you see from the outside if there is a borer in there?
I love my garden.... and Jesus, and coffee, and naps.......
Name: Tom
Southern Wisconsin (Zone 5b)
Irises Vegetable Grower Butterflies Region: Wisconsin Keeps Horses Cat Lover
Dog Lover Keeper of Poultry Daylilies Celebrating Gardening: 2015
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tveguy3
Jul 22, 2014 6:11 PM CST
Sometimes you can see the damage on the leaves, but other times they go right through the center of the leaves to the rhizome and you can't see it 'till you dig them.
I am not afraid of an army of lions led by a sheep; I am afraid of an army of sheep led by a lion. - Alexander the Great
South central PA (Zone 6a)
Irises Region: Pennsylvania
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DaveinPA
Jul 22, 2014 6:32 PM CST
Tom is right, they sometimes leave chewed leaf edges. Also look for frass near the base. In my case the chewed leaves gave it away as frass was only inside the leaf fan. Another clue can be an outside leaf that falls over and is soft on the bottom, but this is also a clue to bacterial rhizome rot as well.

When discovered I removed that particular rhizome, trimmed leaves, started cutting into the rhizome following the path of the borer. Once removed, with damage to its "face" since it did not want to come out, I treated the rhizome with chlorine cleanser powder and replanted it but with no watering in until the cut area was able to skin over for a day or so to reduce chances of bacterial rot. If there are lots of the infested variety I just toss the rhizome.

Thumb of 2014-07-23/DaveinPA/0ebdb4 About 3 cm., just over an inch.

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
Gardens in Buckets Garden Art Plant and/or Seed Trader Moon Gardener Garden Ideas: Master Level Celebrating Gardening: 2015
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grannysgarden
Jul 22, 2014 6:54 PM CST
Gross!
I love my garden.... and Jesus, and coffee, and naps.......

Region: California
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UndertheSun
Jul 22, 2014 7:23 PM CST
Yummy? Blinking

That is one nasty, ugly looking pest! Do they at least make good fishing bait?
Name: Mary Ann
Kentucky
I was one of the first 300 contributors to the plant database! Region: United States of America Hostas Hummingbirder Daylilies Birds
Irises Keeps Horses Region: Kentucky Farmer Container Gardener Celebrating Gardening: 2015
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Muddymitts
Jul 22, 2014 7:50 PM CST
Gross..................
Thoughts become things -- choose the good ones. ([url=www.tut.com]www.tut.com[/url])
South central PA (Zone 6a)
Irises Region: Pennsylvania
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DaveinPA
Jul 22, 2014 8:21 PM CST
Good for bait, but costs you time and energy in extracting them from the rhizomes! Then the "gross" thing is traded for a delicious fresh fish dinner. That is a pretty good trade.
Name: Geof
NW Wisconsin (Zone 4b)
Region: Wisconsin Dahlias Garden Ideas: Level 1 Celebrating Gardening: 2015
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mandolls
Jul 23, 2014 9:44 AM CST
Thanks - the thread got a bit hijacked, but I learned about borers.

I will cut them all back.
Name: Leslie
Durham, NC (Zone 8a)
Region: North Carolina Irises Cat Lover Garden Photography Enjoys or suffers hot summers Celebrating Gardening: 2015
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Lestv
Jul 23, 2014 10:28 AM CST
Not truly hijacked like our forum threads are apt to be Whistling in that borers are related to foliage. Borers lay eggs on the leaves, that then hatch and crawl down the inside of the leaves and down into the rhizomes. To get rid of the eggs is why many people cut back the foliage in the fall. I want my iris to grow as much as possible during the summer & fall so I keep my leaves until October or so, then cut them back. It gets really wet here in late fall so if I don't have a clean garden then the rhizomes are open to rot.
My road calls me, lures me west, east, south & north; most roads lead men homewards, my road leads me forth. - John Masefield
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
Gardens in Buckets Garden Art Plant and/or Seed Trader Moon Gardener Garden Ideas: Master Level Celebrating Gardening: 2015
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grannysgarden
Jul 23, 2014 1:01 PM CST
I never cut my foliage. I pull the dead outer leaves off but never cut into a green leaf. I am not bothered by rot and I have never seen a borer, knock on wood, and hope I never do. I have friends who cut their leaves off when the tops brown a bit so their garden will not look unkempt. I just water during a drought and the leaves seem to be o.k. If our water table keeps getting lower watering habits may change.
I love my garden.... and Jesus, and coffee, and naps.......
Name: Geof
NW Wisconsin (Zone 4b)
Region: Wisconsin Dahlias Garden Ideas: Level 1 Celebrating Gardening: 2015
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mandolls
Jul 23, 2014 2:18 PM CST
I just did a google search and I believe what I have is Iris Leaf Spot http://www.extension.umn.edu/garden/diagnose/plant/annualper...

I have not cut off the dead/diseased leaves in the past couple of years, and we have had an incredibly rainy spring. That explains why it seems worse this year. I am definitely going to cut them all back.

Thanks all for your input.

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