Well, I won't be planting any impatiens this year and maybe for a few more years. I lost all of my impatiens here in PA and in NH last year. Initially, I thought it was due to deer because it happened so fast but, it turns out it is Downy Mildew. The leaves and flowers start to drop off and then the stems just collapse.
The problem is currently in the Mid West & the East Coast and globally and there is no cure in sight. My local garden center will be stocking some impatiens for those who insist on purchasing them but will offer alternative plants that are shade tolerant.
Here is a link to an article that details the problem:
http://www.mnn.com/your-home/organic...omes-hot-topic
New guinea impatiens aren't affected by the disease.
Not good news.