Question
I have grown impatiens for over 10 years in the same spot.  They have always flourished on the north side of our home.  The last three years I have encountered "root rot".  The same thing happened this year.  I fertilize, they are on a mound to promote drainage, and I have changed and added brand new soil this year to see if it was a soil issue.  Once again, "root rot".  What is going on?  When I first planted them in the spring, they looked great for about 4 weeks, then the rotting began.

Answer
Gail,
You don't say what the watering or rain has been like.  Impatiens get rot when the crown of the plant - the place where the plant's stems meet the soil - are kept continually wet.  This frequently happens when watering is frequent and shallow - either hand watering, watering in the evening or water from an automatic sprinker system set to go off too frequently.

In the hottest weather, Impatiens may wilt during the heat of the day but recover in the evening.... but if watereed shallowly they will wilt but also rot because the soil around the base of the plant is too wet.

Plants need moisture but they also need time to dry - water deeply every four days in the hottest weather, and every five or six days if the nighttime temps are cool.  Always water in the morning.  

You could also try spraying the plants and soil with Serenade (Bacillus subtillus) which is  a "good guy" bacteria that out competes the bad guy fungi - spray stems and soil in the AM = and alter the watering so that the surface of the soil around the plants drys out in between waterings.

I hope this helps!

C.L.