The black stuff was more than likely a bacteria or mold you might want to spray a fungicide. This happens when it gets moist around the leaves.

Thanks, Mr Impatiens! The "soot" was even on the lips of the pot,little dishwashing soap and a sponge took care of that, got me some fungicide labeled for roses to spray it with. Thankfully only the walleriana was affected, not the New Guinea ( although I'm carefully looking them over). Have another pot (back home in Florida) with balsamica sprouting. I work in Georgia during the week and need some plants in the apartment ( or I'll get cabin fever). I noticed some of the plants in the complex are covered with this black soot, going to spray the ones closest to my apartment entrance, I suppose I carried the spores in by brushing against some of those plants, they are crape myrtles. Any other tips for balcony grown impatiens? They get afternoon sun for a couple of hours, still zone 8, but in Georgia.
TIA
Enid

I just learned over on one of the other forums that black inky spots are a sign of thrips. I have had this on a succulent euphorbia, and never realized it was thrips. So, if it isn't a fungus then consider thrips.

Jon

Thanks for the further tip. That's it! this means war! I'm getting a systemic in the morning. After Frances and then Ivan I have a zillion "love bugs" laying eggs on my balcony plants, I cant stand them, the winds set them on survival mode, because before the storms we had none of them, we also have all types of moths in the evening and I know the damage moth caterpillars can wreak. Thanks again for the heads up.
Enid

would you all believe this? The infested parts of the impatiens I threw out the balcony landed on a pool of water from a defective spigot. This thing drips constantly. Anyway, every single one of those stems rooted and to aggravate me more they are in flower (mine in the pot have leafed out, but no flowers). I have the notion of going around and recouperating this stuff to put in another pot. They are wet,wet,WET, constant drip on them and perfectly happy growing and flowering against the building.... goes to show you,plants will do what they will regardless of your plans.