It would work here...in Tulsa we grew cacti in cinder blocks. I don't know about Denver, you're a lot colder. If you think blocks would freeze..then no.

I understand that tulips prefer slightly acidic soil and wonder how the lime in the cinder blocks will affect the pH of the soil. I know they will not tolerate the leeching of lime from foundations and figure it is the same for cinder blocks.

I have heard that raised beds for perennials is not a good idea as it changes the depth as to which the frost affects them. Great for annuals and vegetables as they don't need to survive the winter. You might want to investigate this.

OTOH, why not just put them in and let us know what happens next year. (:

jitsmith

I would go ahead and try it, at least with a good sampling of what you plant. I'm guessing you get snow cover most of the winter in Denver?

I've planted many many tulips in raised beds that I was told wouldn't work, and they're absolutely fine.

Same, I've been told that even in my region, I need to lift up the dahlias tubers for storage. But I leave them in every year, in-ground as well as in pots, and they keep returning.

Part of that is just because of what nutsaboutflowers said : try it and see if it works. In my case, I found that doing that to the dahlias does work. So while I am mostly talking about dahlias, I wanted to say that there's no reason not to try something with the tulip bulbs, too.

Does anyone know if this idea worked...in Nebraska and want to try it.....

Sceptical. Tulips need a deep planting or they split off into offsets in their first season. Possible species tulips, since they do very well in pots over several years...but garden hybrids, unless grown as annuals, not really.