I bought a mandavilla last summer and kept it outside at home where it was very healthy with lots of blooms. In the fall I brought it to my office to a large window sill which faces south. It has continued to be be extremely healthy, growing like the proverbial weed, but without a single bloom. It is about six feet tall and growing so much that I think it's going to choke itself out. The only food I have given it is African Violet (liquid) food that is supposed to be for all blooming plants. I've tried nipping all the growing ends but it just sprouts dozens more. P.S. - I was surprised that the tag that was on it when I bought it said it "prefers partial shade".