Tropical-hardy?

Just when I think I have something figured out, I discover I have no clue. Does anyone know what makes a hibiscus tropical-hardy, or what in the world that means? I have attached a link to one found on the Seeds of Life nursery site. I'm pretty sure this one wasn't there last year. There are a couple labeled as "tropical-hardy." I read it says hardy to Zone 4, but then why isn't it just considered hardy like most of the rest they offer? Thank you in advance for sharing your knowledge with me.

http://www.mgbhardyhybrids.com/index.cfm?fuseaction=plants.plantDetail&plant_id=72

They crossed H. moscheutos (hardy) with H. rosa-sinensis (tropical) to get this. I suspected that's what they did, so I googled the name of the plant and found a link to the plant patent:
http://www.uspto.gov/web/patents/patog/week25/OG/html/1307-3/USPP016669-20060620.html
As far as hardiness, I'm not sure I believe the zone 4 hardiness--I'm not sure if straight H. moscheutos is even quite that hardy, and crossing it with H. rosa-sinensis isn't going to make it hardier!

I find it hard to believe that such a cross is possible.Too many genetic differences.Unless the flower was protected from pollinization every hardy flower will self pollinate. The hardy form is herbaceous, the tropical type is woody and shrub like. i need more proof.

Their plant patent isn't good enough for you? LOL I wonder if the patent office requires any sort of information at all for things like this or if they just assume whoever submits the patent knows what they're talking about! That explains why it's so hardy though if it's probably not a hybrid with H. rosa-sinensis. How would you know for sure though--if they kept trying for long enough and very carefully controlled the pollination is it possible that they might have come up with a hybrid between those two? Or is it just too far out for it to even be possible?

The pollen shape HAS to be compatible to cross, even then many things can abort the seed formation. :-) and besides..you can even patent sports.........Whats up with that???Nature made it not a breeder. ...LOL

I tried googling the others they list as "tropical-hardy," but I didn't get the patent link like you did, ecrane. They also list Angelique and Pink Comet, but PF lists those as moscheutos. We obviously just count those as "hardy." Not sure I'm sold either. Off to see what PF says about Cherub.

Cherub is not a cultivar in PF. You guys probably already looked. ;-)

I didn't take the time to look for links to the actual patent for Angelique and Pink Comet, but in one of the google searches I saw that those also did have plant patents (I think they're the same deal, saying they're a cross between moscheutos and rosa-sinensis). But based on what Eclipse is saying, they probably are moscheutos so PF is correct!

Interesting. It's also nice to find out I'm not as dumb as I think I am once in a while. LOL