I have found that my Impatiens grow quite prostrate if they are out in the open exposed to rain. Sheltered under a tree they grow up to about 18" high. I plant about 10" apart for full coverage in part shade. They will not grow as fast in complete shade, so maybe plant them a little closer.

It has been my experience that impatiens don't like living in planters or windowboxes unless the container is really big. I can't tell you how frustrating this has been for me. This year I'm going to try caladium for height (I hope) with some impatiens to complement them. Good luck whatever you do!

How often should I water my impatiens? They are in a windowbox. Also how much water? I am new at this. Thanks!