Neil - I'm growing them indoors, at the bottom of the pot we have the Hibiscus tree in. It's in the church Sanctuary.
As they're in the same pot, I wondered about the differences in water requirements, is all.
Our hardy hibiscus (at home) would not take the dry cold we have here, compared to your wet cold. In fact, we need to water our overwintering plants before the first frost or they would die from lack of water. It's also much more important to mulch overtop before the first snow flies, for the same reason. We don't get the same cold temps you do, however we get 2 weeks of severe -25 in January most years. This past winter was worse than normal, I should add........
