I always trim my irises when I move them but I'm getting mixed messages about whether or not to trim established irises that I haven't moved that summer. Some folks say not to trim them because the dying leaves provide protection from frost but others say to trim them back to prevent fungus and disease. I live near Seattle and our temperatures have never gotten below 0 degrees since I've lived here (seventeen years) so is it better to trim them back? Does the trimming help keep them healthier?

Our Winters are not like yours, so I think it's better for someone with similar weather conditions to answer that.

Many trim [or remove] the spent leaves to prevent moisture buildup near the rhizome. This can be a source of rot and a good hiding place for unwanted damaging insects. I have seen a clump let go for over 6 years with no issues in our moist high humidity environment, but have also seen damage in those not attended to annually.

Do you get any snow? If so it might not be a bad idea to cut them back a bit. There are many iris vendors in WA and OR. I suggest you call a couple and see what they do since they have your same conditions.

Every climate will have it's own effect on the "trim / don't trim" issue. In mine, iris leaves aren't "evergreen", and almost all will be a pile of rotting "mush" in the spring....that lays directly on top the rhizomes ! My thoughts are......trim everything "late' in the season (after we've had several hard frosts, and growth has stopped), remove all the "trimmings" from the beds.....and from the property (i.e. don't compost them..."trash" them !), and , (you may not be able to do this, because of local laws, or the location of the bed), "burn over" the bed. In actuality, you need to find out what works for you, in your climate, and what your "work load" will handle. Irises are quite a "forgiving" plant, and will survive with , little care, no care, and sometimes the WRONG care.....but, that said "surviving" isn't the same as "thriving".

I never cut back my irises during the fall, I just let them grow naturally. But I do gently pull off the dead stems in the early early spring (mid late March) from the last year's blooms. And during the spring summer years, I pull off the the iris leaves that turn a hint of green because they are on the verge of dying. I can just tell when to pull off the leaves because of the texture and color, when good looking iris leaves have a hint of very light blue green and the leaves have a nice thick healthy smooth texture.

The light green leaves is what healthy iris leaves
look like.And the one dark green leaf is what the
unhealthy ones look like. When the leaves turn to
the dark green one, that's when I pull them off because
usually there are new leaves underneath them.


Photo Source: http://www.alamy.com/stock-pho...
(I don't know why my copyright thing showed up at the bottom of the image even
though I am borrowing the image.)

Like what Arlyn said, in the spring the old leaves become rotten mushy on top of the rhizomes. And I do understand, because every spring, I pull the rotten ones out of the flower beds, including the leaves and dead weeds. I call this "Forget the Old and Welcome the New." (F.O.W.N.) Or as what other people call it, Spring Cleaning.
F.O.W.N is where you clean out your flower beds in the spring and it helps your plants breath. You don't want your plants to be covered in last years dead tree leaves and make them sad or sick. You want to make them happy clean and healthy!

Thanks for your comments. I'm pretty good about clearing out the dead or dying leaves in the fall and winter, then doing a spring cleaning as well. My irises usually survive.....but I'm wanting them to thrive and bloom. I've had trouble with getting blooms from year to year and several of my neighbors have the same problem. I was wondering if cutting them back versus not cutting them back would affect their blooming. Also, I live in the foothills of the Cascade Mountains at about 500ft surrounded by conifers which tend to make the soil acidic. Any one else out there that has similar habitat conditions but great luck growing the irises? This year I have added compost and lime to my soil hoping to enrich it and make it sweeter. Hoping for a bountiful spring!!

Lack of bloom can be a lot of things, but often is the result of lack of sun shine, over crowding of the rhizomes, rotting off of the bloom stems, too much nitrogen. With all of the irises I have I simply don't have the time to cut back all of the leaves in the fall. I know people who do that every fall, but mostly for cosmetic reasons. I really doubt if it matters all that much to the irises. I was really late cleaning out beds of dried leaves this spring, and the last bed that I cleaned out had no rot problems at all. I think cutting back the leaves may help with reduction of borer problems though.

I know Tempo Two recommended using lime on the irises - so if you know you have acidic soil, it might be worth a try.

cutting of the leaves gives iris borers less places to lay eggs (Yes, the moth lays the eggs that produce the borers)

tveguy3 said:Lack of bloom can be a lot of things, but often is the result of lack of sun shine, over crowding of the rhizomes, rotting off of the bloom stems, too much nitrogen. With all of the irises I have I simply don't have the time to cut back all of the leaves in the fall. I know people who do that every fall, but mostly for cosmetic reasons. I really doubt if it matters all that much to the irises. I was really late cleaning out beds of dried leaves this spring, and the last bed that I cleaned out had no rot problems at all. I think cutting back the leaves may help with reduction of borer problems though.

Speaking of nitrogen, what type of fertilizers do most of you use? I've read that a 5-4-4 is ideal and for a while I used vegetable fertilizers -- 6-4-4. No help. The past few years I used a fertilizer that the Schreiners Iris Farm folks have developed. That has given me more blooms than previously. But I've read that bone meal and alfalfa meal are good also and less expensive. What works for you???

I do not have many irises, but I have noticed that trimming them is a pain in the...

even my sharpest lopers tend to pretend dull.

So, I rationalize that they have been living a very long time without my help.

Problem solved:)

frank

Sherri, what kind of fertilizer to use is a fascinating and controversial subject. Schreiner's sells 6-10-10.
Superstition sells 6-20-10 with other trace elements. I guess it depends on your soil type to an extent.
My local iris society recommends 10-10-10, which I think is too much nitrogen. I've used bone meal, which I think works fine. I used Superstition's fertilizer to spread post-bloom and to plant new rhizomes last August. Increases are looking very good, so I think Superstition's recommendation is good.

frankrichards16 said:I do not have many irises, but I have noticed that trimming them is a pain in the...

even my sharpest lopers tend to pretend dull.

So, I rationalize that they have been living a very long time without my help.

Problem solved:)

Scissors work well.

frankrichards16 said:I do not have many irises, but I have noticed that trimming them is a pain in the...

even my sharpest lopers tend to pretend dull.

So, I rationalize that they have been living a very long time without my help.

Problem solved:)

I like your attitude!

I mostly use 10-10-10 because it is readily available. I have experimented with that combined with 0-45-0 (creating an effective 5-27-5), but it was costly (money and time) and hard to gauge how effective it was (or how effective I was in distributing it).

If I lived near to Rick & Roger at "Superstition Iris Gardens", I would buy their formulated fertilizer.

For what it's worth, I think the best thing to do is to have your soil tested to see what it has, and needs to grow what ever you want to grow. Otherwise you are just spending money on what may or may not be of any value to your plants. Our water supply is loaded with nitrates due to over zealous users of commercial fertilizers. Mostly on lawns. Any plant will only take up the nutrients it needs, no matter how much of it is available. The rest of it just leaches out into our ground water supply.