I would suspect 4-5 yrs Simbad. They are found in dry woods in Carolina, hence one of its common names Carolina lily. They do look very nice howerever. good growing conditions clearly.

Well done on germinating the seeds. These Liliums have quite a lot of bulb to develop yet before they will flower so I would suggest another three or four years? I would put these pots outside for the moment and keep feeding them dilute liquid tomato feed untill these leaves die off. Then bring them back under cover and keep almost dry until the autumn when they can get occaisional water. Keep them in these pots for the next couple of years them move them into something larger during late summer.

Got the perfect spot for them in a few years time SBG.
Thanks Bulbaholic,amazed they grew, swapped them on a swapshop and they came in an envelope with no protection and being rather large were a bit crushed but ended up with 15 plants so really pleased, thanks very much for the info, will move them outside tommorrow, watch out in three or four years time for flower pics if I can keep them going :-)