Possibly it is one of the stem rot fungal diseases. Over-watering can be one cause, especially in humid or still weather. Copper-oxychloride can help, or remove plants and burn. Don't try replanting impatiens or similar there for a couple of years.
Overwatering can cause the stems to rot and break off.
Yes, impatiens can be trimmed off about half way down their stems making them shorter and more compact blooms.
Deer love to eat Impatiens. They just ate our neighbors Impatiens last night....barely a one left! !
which is a very sall plant with soft stems
They lay their eggs in plant stems rotting wood or wet soil.
Impatiens hawkeri was created in 1886.
Bombus impatiens was created in 1863.
Coprinellus impatiens was created in 1821.
Impatiens platypetala was created in 1846.
Impatiens grow best in part to full shade.
The New Guinea impatiens are a wonderful choice when used as hanging flowers and in the pots.
It depends. I have found that most impatiens prefer shade, and need water, especially if they are in a pot. New Guinea impatiens can take full sun, but again, watering is very important.