Maybe a colder winter with the right amount of moisture? Some years mine just do better than others, and never get as much cleaned up as they need, but unless we have a really hard late freeze, they still do well. I do have some that bloom only every other year, frustrating.

I have grown iris in mulch before, but I actually planted them in the mulch, leaving the rhizome above ground. Much easier to weed. The mulch composted into rich soil. I think if I did not have a lot of iris I would replace the compost as needed, digging and dividing the iris at the same time. Possibly with the mulch heating up, your area might cook them?

We have moved iris in the last two autumns. They did not bloom much last year but look like they will bloom a lot this year. Who knows why.

I'm certainly no iris expert, but I'm thinking the weeds around them probably held in the moisture. The more moisture, the greater the buds.

Debra

That may be because there were weds all around them.

kay

I found Iris to be too erratic. I moved almost all of mine out of the beds last year and into peripheral places around the yard where I will never plant anything else. If they bloom, fine. If not, oh well. I left the 2 blue ones Karen gave me in a bed. One has done well, the other not. If the one that hasn't doesn't shape up this year, it too goes to a peripheral place.

I used to buy iris from growers in our local iris society . Every year they would dig their plants remove any damage/rot , divide and then replant . This was standard practice evidently . It also helps to prevent damage from the iris borer I was told . Anyway here is a link with great info on iris https://www.irises.org/gardeners/care-classification/care/ Lots of good info here .