I bought some impatiens grandis Rosa and hians plants last year. I'd read that they were winter bloomers, so I expected them to bloom under my grow-lights during that season. But, although they seemed to do quite well there, they never set buds. A grandis plant I'd given to a friend bloomed in her sunroom, however. So I concluded that my mistake was probably giving the plants 16 hours of light a day. Does anyone know how much I should give them?