That is very common. Many iris, especially the ones with big multiple blooms, and where there is some partial shade eventually become top heavy and flop over. I end up staking so many each year. I guess it is the result of hybridizing to make bigger flowers.
Laetitia

Laetitia, I don't think lilacs_of_may is referring to typical stalk flopping due to heavy flowers. I think she may be experiencing the same thing that's happening in my beds right now, and I suspect is happening in iris gardens in many parts of the country this year. This last winter and spring's horrible freeze-warm-freeze-warm cycle has had absolutely devastating effects in my iris beds. Not only have I lost huge numbers of cultivars, but I am continuing to lose them every time even the slightest stress occurs: cool temps, rain, wind, etc.

My irises are so weakened right now that almost anything is causing them to rot and/or die. The few that have actually managed to bloom are doing so on very weak stalks that bend or fall with almost no provocation - even the medians! I can count the number of normal looking blookstalks in my extensive iris colleciton this year on one hand!

It's not just stalks, either. Leaves are suddenly falling over and lying on the ground, sometimes with rot, sometimes not. Bearded and beardless. It's just pathetic.

If ever there was a year when I would be inclined to give up irises, this is it. But I'm going to hang in there and hope that a year like this only happens once every decade or so.

Laurie

I have a new garden that is in full sun and I cannot tell you how happy I am with the performance of the iris, even in this wacky weather with the weird freeze we had in mid-April (our TB iris starts to bllom in late April.)

These first year iris were tall, with strong stems. I did not stake a one of them.

Meanwhile, in my "old" garden with increasing shade, they stalks are skinny and sometimes floppy, that is, when they DO decide to bloom.

Sun have much to do with this.

It got down below 40 here for the last couple of nights, and we had high winds. I'm wondering if that was the problem. My Blueberry Bliss may have been knocked over by the wind. The stem bent, and I think that's all for this year. :-(

Many of the other flower stalks are still leaning at 30-80 degree angles. Except for the Bliss, the flowers look fine, and the stalks are straight, not droopy, but they're leaning.

Like I said, I just planted my first irises last fall. Most of them haven't bloomed at all, but I expected that. But this leaning stalk thing, it's just weird.

I stake mine, I agree with njiris, that the very large blooms make them very heavy. My blooms are huge, and must be staked. When I look at irises in other gardens, the smaller blooms don't seem to need the staking. These usually seem to be the common purples and whites. I choose the fancier kinds, and they do bend over. But, I don't mind staking them, they are so beautiful I like them to stand up straight where they can be admired.