When Do I Trim Iris Leaves down?

greekbecky2(6)September 18, 2010


Just a simple question here...When Do I Trim Iris Leaves down 6 inches?

Thanks in advance!


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I never trim bearded iris;
they remain green all winter, storing energy in the rhizome for next spring's bloom.

don't know about other kinds;
the only other ones I've managed to grow are Dutch & Spuria, & both of those wither & die off by themselves.

    Bookmark   September 19, 2010 at 5:00PM
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hosenemesis(SoCal Sunset 19 USDA 8b)

I don't trim my bearded irises either. I pull off the yellow and brown leaves and leave the rest so that there is some vertical interest in my garden during the winter.

    Bookmark   September 19, 2010 at 10:00PM
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I tend to agree with both of you (I never trim them either), but I read somewhere that towards end of fall, you're supposed to. I had a bad problem with snails climbing up the leaves this year and now 50% of my leaves are dotted with dead spots (brown) where I guess they bit into them, the rest of the leaves are a nice green. Its not a big deal, just a bit unsightly, so I figured if I read it somewhere it would solve the problem. Winter will be here soon enough, so that'll so my problem. I'll just let them be...:)

    Bookmark   September 19, 2010 at 10:56PM
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ken_adrian Adrian MI cold Z5

i was told.. due to iris borer . that they are to be trimmed down in fall ... to remove the layed eggs ...

my theory is that i will do it.. after the first hard frost.. so that i am more sure that the darn iris borer moths might actually be dead.. and all eggs laid... so that i might actually remove them ...


i speculate that if i do it too early.. wont the moth just come along and lay them on the new cut part ..

yes or no??


    Bookmark   September 20, 2010 at 12:53PM
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hosenemesis(SoCal Sunset 19 USDA 8b)

Sounds like a great plan, Ken. Can you report back on what happens? Here in Socal we don't have the borer and we don't get hard frosts, so it may be beneficial for us to leave the leaves on. But in your climate, I don't see why you should, if the eggs will be overwintering there.

    Bookmark   September 20, 2010 at 3:46PM
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kentstar(5b, NE Ohio)

Mine eventually go all brown over the cold winters here anyways, so I just pull them off as they go brown. I don't ever trim off the greens though.

    Bookmark   September 20, 2010 at 9:10PM
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East of the Mississippi River iris borers can pretty much wipe out a bed unless controled. I cut the leaves down to about an inch or two from the ground in late October or November--anytime it isn't too cold to freeze your fingers. I pull any dead leaves completely off. Then I burn them in my fireplace. It seems I heard the moths lay their eggs in late August, so by October you should be safe. In early spring I spray with malathion or sometimes I use a systemic rose fertilizer with insecticide built in. I used to use Cygon, but it has been taken off the market. Since I now have bluebirds nesting in my garden, I haven't been using insecticide the last two years, and the cutting off of leaves and clearing the ground has helped immensely. I have found that mulching with 6" of clean rye straw over the winter is also very beneficial where I live near St. Paul, MN, but be sure to remove the mulch in the spring. I envy those of you who live where there are no borers! Northwoodswis

    Bookmark   September 21, 2010 at 12:54AM
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I changed my mind, I think I am going to try your process of controlling the borers. I really haven't noticed any, but better safe than sorry.

    Bookmark   September 22, 2010 at 11:31PM
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hocasati(Willamette Valley Z6)

OOPS! I have no experience with TBI. I'm in Z8. I just trimmed them all back this afternoon. I thought that's what I am supposed to do. I noticed even the blades when cut it has a fragrance like the flowers.

I didn't see any blemish or anything eating the leaves. They were perfectly healthy.

What will happen to my TB Irises?

    Bookmark   October 2, 2010 at 10:35PM
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hosenemesis(SoCal Sunset 19 USDA 8b)

They'll probably be just fine. Some people cut them back to about eight inches every year just to get rid of the ratty foliage. It may take them a bit more energy to produce new foliage, that's all.

Don't give them high nitrogen fertilizer. That may cause them to rot.

    Bookmark   October 3, 2010 at 1:57AM
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Where we have frost and freezing I think that cutting then down is better than watching them be flattened by the snow.
Can anyone tell me how far apart the bearded irises should be planted for the best sucess?

    Bookmark   October 7, 2010 at 9:23PM
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hosenemesis(SoCal Sunset 19 USDA 8b)

Most growers recommend planting them 12 to 18" apart so you do not have divide them for three or more years. I always plant mine far too close together (3") and regret it the following year, since I have to divide again and it sets back the next bloom. Do I ever learn? No.

    Bookmark   October 7, 2010 at 11:41PM
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