I find myself in that situation with my Rebloomers. Another option. If there is nothing around to cross to is to cross it to itself. I have not had success yet but I only tried once. Last December, Lichen had a healthy seedpod and I didn't cross it and there had been no other blooming Irises for awhile, so either the wind or some tough little bug crossed it. Sadly, we had a few hard freezes and the mysterious seedpod wasn't able to reach maturity.