Yes. I collected the seed from mine lasy year and about a month ago I put about 50 in a seed tray and left it outside. They've almost all sprouted.

I've collected self sown iris in the past and they make a decent sized plant in a year and usually flower in year two or three

Here are some photos of the sprouted seeds I sowed recently and the iris the seeds were from

http://www.flickr.com/photos/31559373@N00/7746003272/in/photostream

I guess the seeds need to be left to become fully ripe (i.e. not green) before planting?

Yes. They go a brown colour and then you can sow them

Thank you - I will give it a go.

Leave them in the pods until the pods are dry and the seeds should then be ready

Remember that it will take 2-4 years for the seedlings to bloom.