Veronica seeds - how and when?

My veronica longifolia 'Blue Charm' are still blooming, but many of the heads are about spent. How and when do I collect the seeds from these plants?

Vols the little round bead-ish pods will vent open when the seeds are ready. Then the whole flower stalk can be cut and tipped into a bag or container. The tiny seeds fall right out. I have an unimproved veronica that makes TONS of seeds but I've found that a lot of the hybrids don't make any. I'm not sure about blue charm - If the seeds don't spill out easily I'd say it's probably sterile.

Thanks, Sue. We'll see what happens!

Sue
Thanks from me too. I've got some Sightseeing Mix plants that have the bead like pods and was wondering when to collect them. do you know if Goodness Grows is sterile? I saved the spikes, but haven't tried to plant any of the seeds.
Cala

I'm gonna throw in another veronica seed collecting question here. Today I deadheaded all my veronica and tried to save seed from Blue Giant and Icicle by holding the stem with the 'seeds' in my palm and then pulling the stem while pinching with my thumb so that all the chaff and hopefully seeds fell into my palm.
How big are veronica seeds? . sized or * sized?
I'm thinking of trying to damp papertowel sow a pinch to see if anything sprouts, cuz it all just looks like little bits all the same to me, so maybe they were sterile. Or maybe they had already dropped seeds before I got to them. New to saving anything other than big seeds.