Thanks for your research. I must admit that the one I saw actually had zone 5 written on it. Funny how they don't specify Canadian zone 5 or USDA, especially when so much stock sold here is shipped up from the states. Makes you wonder why they would bother to stock something like that at my local Canadian Tire, and Loblaws. I guess they haven't figured out the zone thing themselves. On the experimental side I have actually overwintered a Hibiscus Syriacus Blue Bird for about 10 years, but then one year at the height of 7 feet tall she died. I'm sure Blue Bird is a Canadian zone 6, possibly 7. Although I'm trying babies from the Blue Bird only one has overwintered two winters (so far) and so that is why I'm looking for a hibiscus that is more hardy in a purple, but with that kind of height. So, Lavender Chiffon likely isn't any more hardy than Blue Bird. I'll have to see how lucky I feel when I see it marked down. Mary

Rose of Sharon (H. syriacus) is a woody shrub, and quite hardy. These often have very fertile seeds and you can end up with a forest of seedlings coming up near their parents if you're not vigilent. Many folks don't like them due to this "weedy" aspect. There are much improved modern varieties available. I've been especially pleased with the hybrid 'Diana' that was a USDA release several years ago. No seeds and very large, flat white flowers and blooms 'til frost. It is easily started from cuttings during the late summer. The hardy herbaceous hibiscus is H. mosheutos or one of it's many hybrids and varieties. I'm not sure if any of this species can tolerate Z4-5 winters, even with a heavy mulch. The evergreen tropical hibiscus that you see in Florida, Hawai`i and other warm areas is H. sinensis. These will not tolerate cold.

If you want to have your ROS somewhere else in the garden, I find that it is easy to make cuttings. These could be planted where you want them to be. Then you could remove the original troublesome bush. IF you want to kill it, there are some herbicides out there that will certainly take care of it. Round up works wonders on killing the plant, as does straight javex. When I was young, I recall my dad wanted to have the city remove a dying maple tree from the city boulevard, and they refused because it was not dead enough. A few copper nails worked wonders, and the next year they removed a completely dead tree, as he smiled from inside the house.

I just bought a couple of ROS at the Bluestone Perennials 50% off sale about twenty minutes ago (gotta convince Hubster that I SAVED money, not SPENT money!), so I just read about this very subject. ROS seems to bloom its butt off with very little water; other than when they are first planted and getting established, they don't need supplemental watering at all unless it's a heavy drought. Given that, I would think that they wouldn't compete much with the hostas. Also, the ROS root system shouldn't extend beyond its dripline, so unless your ROS is going to be HUGE, I don't see a conflict. I'd love to see pictures when you're done!