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.

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.
Renee

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...:)

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 ...

ANYONE AGREE WITH MY THEORY???

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??

ken

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.
Renee

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.

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

Northwoodswis4:

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.

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?

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.
Renee

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?

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.
Renee