Harvesting seed pods from your iris plants is bound to be beautiful, but may not be what you expect... The genetic makeup of individual plants is such that unless you are entirely sure that you have "true-type" irises that have only been self-pollinated, then the seeds that you harvest and plant may not necessarily look the same as the flowers that they come from.

In other words, you may be currently be enjoying the blooms of a peach or white-colored iris, but when you collect the seeds and plant them, it may be a pink or purple (or any other color) iris that blooms. The only way to propagate the parent plant and maintain the same appearance is to dig it up and divide it. I have included a video at the end of this posting, should you decide to pursue that option.

In order to harvest the seed of a Siberian Iris, you simply have to let the flowers bloom and die off. As you watch them wilt, keep an eye out for seed pods forming on the end of the stalks- these seed pods will start out green, but gradually become brown and britle, and then eventually split. Once the seed pods have split, look inside- the seeds are dried out and ready to be collected when they are dark brown and glossy-looking. Seeds that are green should be left to "cure" in the seed pods until they appropriately dark brown.

Hold a small cup or bag underneath the dried-out seed pods and carefully cut the entire pod so that it drops into your container. Seed pods that have fallen onto the ground can also be collected, as it is likely that they are sufficiently dried out. Now, take your collected seeds into a well-lit place, and remove the dark brown, glossy seeds for saving, discarding the grey or white seeds. Clean them of other plant matter and store them in a labelled envelope in a cool, dry place to let them finish drying.

Here is a useful video that demonstrates dividing a Siberian Iris:
http://www.gardengatemagazine.com/81dividing_irises/

Good luck!