All the bearded iris vendors take orders just about anytime but they are only shipped in July. So It doesn't much matter when you order them, you get them in July. I never gardened in a zone 9 so can not give you any advice on growing Siberian Iris in your zone, but it might be too warm for them.

Hi aimeekitty,

Siberian iris are tough to grow in California. There is one variety called "Caesar's Brother" that may live.
Spurias and Louisianas will do very well here, but the LA irises like moisture.

Order now for July and August shipment.

Be sure to check out the rebloomers. Here's a link to a grower that specializes in rebloomers.
Renee

Here is a link that might be useful: Stanton iris

Thanks Renee, that's exactly what I needed to know! too many of the sites I found via google were too vague about where they do well and what the planting times were. Much thanks!

Renee,... so... sorry, a little confused. So do the reblooming bearded ones listed on that site do ok in SoCal? They do, right? (I'm sure I've seen bearded irises doing great at Huntington Gardens...)

Also, are there any recommended sites for buying Spuria or Louisiana irises...? (like is there a west coast supplier?) Much thanks,
Aimee

No reason siberians shouldn't do well in SoCal - they don't mind the heat -- it's just summer humidity that might limit their growth and that's not a common issue in most of CA. I'd also look at both sino-sibe and cal-sibe hybrids in addition to west coast species iris and Pacfic coast hybrids. All are very easy to grow and many will be evergreen in your climate as well. And they offer some rather unique and intricate flowers compared to the more common bearded varieties. The San Diego iris society should have links to local suppliers (and there are MANY in CA).