Transplanting iris - cutting back?

I have heard two different things about transplanting iris - cut the foliage back so that the plant can use its energy to develop a good root system, and leave as much foliage as possible so that the plant can make energy for the rhizome.
This seems to be two different ideas???

Does every new blooming stalk for next year grow from a new rhizome, which grows new roots as it expands? I have ordered a couple of iris books that I hope will answer some of my incessant questions! I gues what I am saying is, when I divide iris I usually let them sit out for a day or so, and the roots get all dried out, but I can see new root buds beginning to form. Do the old roots revive also?

It's generally considered best to cut back only enough foliage to prevent the plant from tipping over when it's replanted. Cutting back more won't promote additional root growth. In fact, it may delay it while the plant regrows enough foliage to feed itself.

If you have divided a clump, it's a good idea to allow the divided rzs to dry for a couple of days before replanting to give the cut wounds a chance to scab over so they won't be so vulnerable to bacterial infection. The existing roots will dry out a little, but they'll recover after replanting (assuming you don't wait weeks or months to replant). Even if the existing roots die off completely, new roots wil quickly emerge from the replanted iris.

Some folks shave off all of the old roots before replanting, but I've never seen the sense in that. I'll leave the old roots on even if they're completely dead and shriveled because they'll still help anchor the rhizome in position while the new roots are growing. I hate it when sellers cut back roots to an inch or two. I like long roots to help hold new transplants in place, which is why I leave about 4" root length on the irises I sell to other folks.

Yes, every new bloom stalk grows from a different rhizome than the rhizomes that have bloomed before, and rhizomes do continue to grow new roots throughout their productive lifetimes.

Laurie

Thanks, Laurie,
I like to have the roots to use as anchors also, and I appreciate your generous sharing of your experience.
Even though I want to grow some of my iris in the general mixed perennial beds, I think I will be digging up some beds for irises planted in rows, just to make it easier to grow and care for them. To be able to walk all around and deadhead, etc.

After visiting wandasflowers in CR I learned a valuable lesson on dividing iris. Wish she was here to explain it to you.

Med. size rhizomes will usually produce a bloom. Very large ones(the mother tuber) will either die or send out several babies which won't bloom the first year, but may take 2 or 3. years to produce. It's some of the discount places that offer these huge roots for sale and often it will take up to 3 years for them to bloom.

Last summer I thinned out a bed of Immortality. I put back the largest, most developed roots and had 1 bloom there this spring. I threw away the real scrubs and planted about 20 med. sized rhizomes together for the mg plant sale, but didn't get them potted up so they bloomed there this spring. Most blooms (about 15) where the smaller rhizomes were planted. Live and learn.

This message was edited Jun 10, 2006 7:22 PM

jamlover, I think you may have misunderstood what Wanda told you. It's not that larger rhizomes won't bloom. It's that rhizomes that have already grown to blooming size and bloomed once during their lifetimes will never bloom again. Those are the "mothers" that will produce baby rhizomes and/or eventually die. However, large rhizomes that have never bloomed still offer the best bloom potential for next season.

Laurie

Interesting. I suppose you can tell rhizomes that have already bloomed by the remains of a bloom stalk? I am going to do some close up drawings from life to study these things. It's fascinating, don't you think?

So, a rhizome only blooms once!! Then do some require 2 or even 3 years to reach blooming size?

Yes, every rhizome only blooms once in its lifetime. In most cases, a rhizome will also grow new little rhizomes (increases) along its sides. It is those increases that will grow and mature to blooming size and then bloom and create increases of their own. That's how a single rz turns into a clump over several years. The bloomed rzs (mothers) will eventually exhaust all of their energy and die. The year they bloom, you can identify them by the old bloomstalk, but if they survive another year, they probably won't grow any foliage to speak of the following spring. When you take a really close look at your clumps that have bloomed this year, you'll see that it's quite easy to identify the bloomed rzs even if there are no old bloomstalks remaining. An unbloomed rz will have a full fan of leaves. A bloomed one will not.

When you dig and divide a clump, you may choose to replant the old mothers in hopes that they will continue to produce increases (which they may or may not), or you might choose to trash them if you don't want to wait around for new increases to mature. As I mentioned before, your best potential for bloom next year will come from the largest unbloomed rzs in the clump.

The speed with which an increase matures to blooming size depends on the length of your growing season, your specific growing conditions, and the cultivar itself. Some irises (notably the dwarfs and smaller medians) may mature increases in a single season even in my short-season climate, while some TBs have taken as long as 7 yrs to mature increases to blooming size in my garden (more typically 2-3 yrs for the TBs, though).

Indeed it is fascinating.

Laurie

Very enlightening, Laurie. You've explained a lot here. So, does the mother rhizome also add energy to the developing rhizomes, or does it just give birth to new ones? So when we divide our clumps we are mainly allowing room to grow for the young rhizomes, right?
And getting rid of rot producing over crowding and diseased areas...
I've ordered two iris books from amazon - last year it was daylilies, this year is the year of the iris!

This message was edited Jun 11, 2006 6:25 AM

The mothers will continue to feed their increases as long as they can, so it's best not to remove very small increases from their mothers unless the mother is diseased.

Dividing prevents overcrowding and provides the opportunity both to remove dead or diseased rzs from the clumps and to amend the soil before replanting.

Laurie

So if a clump was just saturated with blooms this spring and the area is thick with large rhizomes it is probably time to divide? I have a crowded looking clump which I was going to divide (or so I thought).

Maybe, maybe not. Generally folks don't get around to dividing until they notice a diminishment in bloom, but if you want to get ahead of that inevitable occurrence, you can divide now. I had LOTS of clumps that were covered with blooms this year, but I'm only going to divide the ones that are crowding their neighbors.

Another option is to dig up only about half of the clump so that you still have a nice sized portion of the clump that hasn't been disturbed that'll give you good bloom next year.

Laurie

Good discussion___ with every plant it is so different. Had a few iris for years but just divide about every 5 or 6 years and watch them flower.

You mentioned a full fan of leaves. How many is a full fan?

Hmm. That's not an easy question to answer. Immature rzs will produce fans with fewer leaves than mature rzs, and a mature TB fan will generally have more leaves than, say, an MDB. As a general rule, the more leaves in the fan, the more mature the rz.

If you're still wondering how to tell a bloomed rz from an unbloomed one, just go take a good look at your clumps right now. You'll see the difference in how the fans grow on a rz with a bloomstalk and those without. When you dig the clump, you'll also see what the old mothers (older, bloomed rzs) look like. They'll have little or no foliage and few (if any) viable roots of their own.

Laurie

Now all I need to know is - where am I going to find the room for all of my plants once I get into dividing as well as acquiring more??? ;>)))

One year I took hundreds of extra rhizomes into my county extension service and had them offer them free to area gardeners. They were all gone within two hrs!

Laurie

I was thinking maybe the local farmers market. My beds are all getting so crowded - not just irises, but sedum, rhubarb, other perennials, etc. I don't want to take as much time with it as you do Laurie, selling over the internet and having to ship plants, etc.

Unfortunately, I can't sell irises at my local farmer's market. Our FM is held in the Wal-Mart parking lot, and Wal-Mart won't allow sales of anything in the FM that they sell in the store. I don't know what's going to become of the FM when Wal-Mart becomes a Superstore with a grocery, which is supposed to be happening soon. I suppose the FM with either have to move then, or Wal-Mart will have to change its policy regarding competitive products.

Laurie

I'm trading some rhizomes, and this is the first time I've done that. What should I be looking for, in choosing ones to send?

Also, I have some huge clumps that look very crowded to me, although this year many of them bloomed. Should I break them up and give them some room, or not?

When trading or selling, you should send the largest unbloomed rhizomes you have.

I've already answered your other question in a previous response to this thread.

Laurie

Haven't you driven along a country road and seen iris coming up in the ditches? They multiply so much I give away what I can, replant no more than 6 to 10 rhizomes of a clump and into the ditch with the rest.

Maybe a stash near a road sign would attract somebody!!!! I have several of Mom's from the 60's that are the larger flowers, not the real historics with smaller blooms, but no names unfortunately. jam

There are 5 irises that came with our farm - survived for years totally uncared for. They still come up from rhizomes I have set under bushes to be planted out later - and then forgotten. But the newer and more choice ones don't seem to have the same tenacity. Actually, though, the old ones get all spotty-rotty too, except they just keep producing new rhizomes on top of the old, and I don't expect too much out of them...

You mean that we might want to try another drug drop, Jam? Except that our drug of addiction this time would be irises, rather than dahlias? Sounds like a plan :>)
What colors are yours? The dahlias I found under a road sign are all coming up!
Sharon

I can make the rounds of the clumps and detach a rz or 2 anytime. Right now I kind of know where the various colors are. Later this summer I may not remember.

Yeah I know what you mean, but here's an idea that I just started to use: Write the name, (or color) on several leaves with a sharpie. It should still be there when you go to divide them. This is especially good if you have several different ones that have kind of grown together - if you mark the leaf on the bloomstalks, you should be able to untangle the colors.

Good idea___I can do that now and dig a little later.

Terrific idea on labeling irises right on the leaves, I too have a bunch that need to be moved later.
Right now I am preparing for my sister's wedding which is going to be held in MY GARDEN!! I have been busy "threatening" my grass with Round-UP if doesn't grow. The challenge I face is that I just finished a huge remodeling project and my entire backyard was demolished. I had to somehow use some very large foundation stones that were removed from my house as part of the renovation. The solution was to terrace the yard using these stones. So, I have a lot of new garden beds to create. As a stop-gap, last fall, I just threw any kind of perrenial seed packets I happened to have received free from real estate agents and gardening clubs - There is a bunch of stuff growing, some things I recognize some I don't. I am afraid to weed too agressively for fear of pulling out some good stuff. Will post pictures as things progress. Here is a picture of the foundation stones that were removed from house (110 years old).

Here is a shot of my backyard during the demolition phase.

This was taken as the hardscape was being done. You can see the new extension in the back with the bay tower. More to follow when there is something more aesthetic to show.

What an exciting project you are embarking on! I just hope that your sister's wedding is a reasonable ways away in the future! Yes, keep us posted,
Sharon

Thanks for posting your photos, and please keep us updated.

Sandy