I have had this happen with crinum and cymbidium orchids and it has been 1. grubs inside the stem eating it 2. snails slugs. It has always been near the neck of the stem - never lower down. They dont seem to eat all the way through, maybe a reason, maybe just luck. This could be your problem. I have read that there is also a mineral deficiency (cant recall what) that can cause a flattening and partial split in the flowering stems of plants. This can happen to gerberas. Some possibilities for you to explore further. Robyn

Anyone know any good web sites about irises? I've been Googling and can't seem to come up with the appropriate site for this problem.
Cheers,
Dee.

If it is bearded irises, it may simply be the cold/frosts. It is too early for them to be blooming here at least, and any early buds will just rot or the stems collapse.
If you mean dutch iris, then it may be as Robyn suggests.
www.irises.org takes youto the American iris society home page, with links to iris growers and clubs around the world.
Also Impressive Irises in South Aus. has some useful information on their web page.

Here is a link that might be useful: Impressive Irises

Thanks Spraxis. This particular clump of irises has been blooming happily for a couple of months now. Then all of a sudden this started happening. Btw, they look like a bearded iris but are fairly small with a deep purple flower.
Cheers,
Dee.

There is an older type that starts blooming in March and continues for some time. Has a smaller flower, on shorter stems, dark petals and a white beard. Grows in the gardens in Castlemaine.
Colleen Modra from Impressive irises puts it down to wind, and moisture collecting in the fans. Sounds likely to me. Frost is my biggest enemy at this time of year - if you get an early bud it opens in the fan, instead of growing into a tall stalk, or it aborts altogether. I have one now trying to bloom. These problems don't generally occur with the dwarf beardeds, which are much more cold hardy.

Sparaxis, thanks for your help. I'm not sure about the frost, because we haven't really had any to speak of and the flower is opening at normal height. My iris doesn't have a white beard but sounds like what you described otherwise. I don't know anything about it, I can't even remember where I got it from. I'll check out those links you gave me...I just haven't had time yet.
Cheers,
Dee.