Think it is possibly a little early to divide yet RHS recommends waiting 6 weeks after flowering to do. When you do lift the whole clump and cut away each fan of leaves from the clump, using a sharp knife. Each fan should have a portion of young rhizome. Select the largest fans with the healthiest rhizomes and discard the rest. Shorten the leaves to about 15cm above the rhizome and trim the roots to shorten them too. Then replant as normal.

Each rhizome only blooms once, then produces a "daughter" rhizome. The outer ones are the best ones to plant.

That is a new one on me Bathgate. I am sure that the clumps of dwarf bearded ones in the garden flower on each rhizome, every year and they have never actually been split up, only bits taken from the outside for propagation.
Also some of our big ones have only ever had one fat juicy rhizome which produces a flower each year, but no new baby rhizomes.
Agreed that after about three years the central one is shot at and should be discarded.

There are some re blooming varieties but those aren't guaranteed to bloom a 2nd time.

Once a rhizome has bloomed, that rhizome will not bloom again. Only the “increase” rhizomes that grow along the edges of the “mother” rhizome will bloom, so save the “increase”. Discard all the other rhizomes and leaves by placing in the curbside trash can. Do NOT compost iris plants. https://www.mastergardeners.org/digging-dividing-and-replanting-bearded-irises

I shall have a word with Claire Austin, THE Iris grower and ask her opinion about this. I have to say that I have never heard this before and we have had no trouble with flowering each season with all the rhizomes, not just baby ones.

I agree...

I agree the rhizomes produce flowers for more than one year... we witness this in our garden - where did this info come from Bathgate?

I've already referenced a source, just scroll up.

Most of the stuff in that 'source' is completely rubbish for the English Lake District. Feed in February ughhhh!

Bathgate, please remember that UK and US growing conditions are very, very different. I always look to see where the person asking the question is from before I jump in with both feet!

Mg - An iris is an iris whether it's in UK or US. That shouldn't change the nature of the plant itself. Bub It's fairly common knowledge.

Choose which rhizomes to plant. A rhizome will only bloom once in its life. Its energy then goes into producing daughter rhizomes that bloom in their turn. Larger rhizomes can be cut away from the mother rhizome and planted on their own. They will bloom in a year or two. Planting a mother rhizome with nubs and little rhizomes attached will give you a blooming clump in a few years.

Read more: http://davesgarden.com/guides/articles/view/123/#ixzz3eUXoxDpV

Bathgate all the books I've checked do not say that the rhizome only produces a flower for one year... sorry I think you are wrong!

Oh and apologies to Richierich123 as this questions has become contentious!

Mg, i'm finding the exact opposite on my end. I just listed another source above. There are also videos on YouTube.com https://www.youtube.com/watch?v=O5ZZ_PvNcws

So far that's three sources I've given you with consistent information. There are others too. I'd like to check your your sources if you can list them for me.

We both can't be right, I'm just trying to get to the truth. I have several patches of Iris in my garden. This is the main reason I divide them.

Mg. I don't feel we are being contentious. If I'm wrong, I want to know. Have I been dividing my irises in vain?

Well we only divide when they have become to tightly clumped together and have then select the best looking rhizomes to grow on but it certainly isn't something we do every year. Unpotting and repotting the Juno Irises is a big enough job :)

thank you :)

Sorry I was not more specific and mention the variety of iris I'm asking about.
It is the tall bearded iris 'Braithwaite', but maybe the same way of dividing applies to all?

Seems like I've opened a can of worms here! But looking on Google, everything that 'Moon grower' says is correct ...

Talking from my own experience, irises struggle in my very dry alkaline garden. I have a small clump of a lovely blue bearded iris which has never been divided and hasn't increased at all over about 15 years. It still flowers each year. It gets dug up occasionally to keep it near the surface and the rhizome looks exactly the same as the day I planted it! If I wanted to propagate it, I would do exactly as MG says in the first reply.

Richierich the advice I put up was specifically for bearded iris... so it is your choice whether you want to divide or not.

I have just checked back on the first reference and the writer is talking about Santa Clara County. Forgive my poor knowlege of American geography but is this not in the hot and sunny part of California?
If so, growing conditions are very different to the British Isles, particularly Cumbria and Scotland where we vie for the title of coolest/wetest summer.
It is very possible that in Santa Clara bearded irises are monocarpic, I don't know, but in our gardens each rhizome would appear to flower for several years. They put out daughter rhizome from the center, which eventually dies, but we only divide every five to ten years and only then if necessary.

I don't wish to belabor this any longer. I've sited 3 references to support my point already. I'm in New York, not California.

Very different!

Yes and California itself varies vastly among the different regions, Napa Valley vs Santa Monica.

Have read all this with interest. My mother never divided ours and they bloomed every year regardless of what the references say. I would trust what I had seen happen over what somebody had written should happen.

I have to respect the education & wisdom of those who specialize in growing and dividing irises. They've been doing it longer then I've been alive.

Also certain individuals on this site (GoY) look for any chance to cut me down or make snide & insulting remarks - even though they have no particular point to make. They are just bitter unhappy folks and very envious of me because of who I am and where I'm from. That just makes me smile.