Dierama

You can propagate these from off sets , but I don't know about seeds

Yes, the seeds germinate very easily and quickly, but they can take quite a few years to get to flowering size - I did a blog on mine last year. I wouldn't try the offsets myself as I believe they don't like root disturbance.

I've grown Dierama pulcherima for years. They will germinate easily but they really don't like being transplanted. They really hate spending the winter in pots. The answer is either to sow them where they are to flower, or to sow them in deep pots like you get roses in. Sink the pots into the soil over winter. In the spring, thin out all but the strongest seedling. When it is a good size, prepare the planting hole the right size for the pot and then slip it out of the pot and into the hole without disturbing the soil in the pot.
Hope this helps.

Thank you all so much. They are so beautiful - but they sound difficult. Worth a try though.

No, not difficult. You'll probably get a few seedlings if you just let the seed fall naturally.