Hmm, hard to say - I've checked everywhere I can, and its said Carex generally can be grown from seed, but they don't mention Sparkler as being viable from seed. I've certainly had seedlings of the browny beige version pop up uninvited. It might be that this is one hybrid which doesn't come true from seed, and certainly I'd have expected the variegation to be showing by now - unless you've had them somewhere with no sunlight, possibly, but even then, you'd expect to see some variegation, even if not very obvious.

No I couldn't find any info either Bamboo, I too have several other varieties that self seed and always come true so this one puzzled me, they're in a sunny spot in the greenhouse, maybe grow them on a bit more and see what happens,thanks for searching for me :-))

No, wont come true from seed, this is a cultivated variety and needs to be propagated vegetatively, ie by division or cuttings which isn't easy with this form. Also not hardy and needs to be kept frost free through the winter.

Thanks Spruce thought some clever person on here'd know:-), looks like these are destined for the compost then, did manage to keep it frost free for quite a few years by putting in the sunroom overwinter but obviously last year even in there it was too cold, shame it was a lovely plant.