I've heard that viviparous lilies are harder to get to make tubers/corms. I've tried Blink 3 times now, even had a decent sized parent plant last year. It failed to make tubers & I have a hard time getting even decent sized viviparous starts to prosper. So I don't know what the trick is in getting it survive. I also had a bunch of Islamorada plants, even blooming size that didn't survive this past winter since I didn't have enough room to put them in one of my coldframes. I've found with young viviparous plants in dixie cup sized pots that I'm able to get them to come back the next year if in my warmer coldframe. It could also be that I'm giving too much fertilizer to the parent plant & it doesn't feel it needs to kick into survival mode.
With any new tropicals I'm getting in, I start them out in a small pot with very little fertilizer (sometimes no fertilizer) in hopes of crowding it/starving it into that survival mode of making corms.
I had ordered some lilies one year & when they came in they had HUGE long growing stem (not sure this the correct word for it) & I planted them in big pots in order to fit their root system. Big mistake. They didn't tuber & what I probably should have done was float them in order to try to force them into making tubers.
Did you know that if you get viviparous pads with well developed nodes you can baggie them with pond water & a decent sized air pocket, float them in the pond, change the water every couple days, & you'll get faster growth of the viviparous part of the pad?
Hopefully Sean, Craig, or someone one with more experience than I will chime in to help us get our viviparous lilies to corm/tuber better.
BTW, Ostara does tuber/corm easily.