I've recently purchased two bougainvillea from a woman who moved them to Oregon from Hawaii. They were not flowering and looked rather sparse, but I bought them anyway. I repotted them in soil that allows for good drainage and put them in front of a big south facing window. Since then they have started losing their leaves quite rapidly. I've searched online but can't tell if this means they're dying or if this is to be expected in the winter. Should I be cutting them all the way back like it's a geranium? Should I leave it alone? Is there another trick I could try? Anyone have any ideas? Thanks very much.