Here's what *I* do. I add equal parts potting soil and PEAT MOSS. 1 part of each and mix well. The peat retains moisture thereby reducing the amount of watering you have to do. I do this with all plants that are like impatiens when it comes to watering.

Tom

The impatiens that take the worst beating are those that are getting that hot afternoon sun. Those that I have planted in direct sun until mid afternoon are flooded heavily like they would get if we had a big fat thunderstorm, and that usually lasts a good three days. Maybe a soaker hose would cut down on your time having to water them? Tom's idea about soil additives is an excellent one too. There's also a product (I think Lowes sells it) that is similiar to what they use in disposable diapers to retain moisture- sorry I can't remember the name of it for you.
-Nan

Probably too much sun. They just don't like it.

Zone 8 is pretty hot for impatiens. Mine on the front porch facing south with some western protection wilt every day during the late morning/2PM timeframe, then they come back.

My only other comment is you have to water container plants every day if it's particularly hot or they get alot of sun. What kind of pots do you have? I've found the plastic or fake clay ones hold moisture so much better. Terra cotta planters wick the water out of the soil and it evaporates - good in some ways so you can't overwater, but in hot weather, it makes it necessary to water daily. My hanging pots in wire/cocoa mat baskets need watered sometimes twice a day as they're in full sun.

I'm in NYC where our summers are tough on plants that require a lot of water. I have a pot of Impantiens in the roughly the same conditions you mentioned -- 6-8hrs. or so of full sun. What made a HUGE difference for mine was mulch. A thick layer of it. Not the large one. I use the cedar mulch which is more fine and doesn't allow much evaporation to take place. My Impatiens has never slumped over. You might try that.

They also MUST have water every day. I water mine in the evening so they have many hours of recovery time from the heat of the day. They get watered until there is run-off from the bottom of the pot. I found out the hard way that just because it rained, it doesn't mean the plant got enough water. Sometimes the foliage of the plant gets so thick that rain water doesn't necessarily reach the soil in ample amounts. I learned to check the soil after rain to see if it was actually damp -- and to my surprise it wasn't more often than I care to count. Even easier is to pour water into the dish the pot sits in, if it starts to get absorbed, the plant needs to be watered.

Also, along with the comment about clay pots... I would add that using light colored pots is better, too. It doesn't heat up like dark colored pots do. As the pot heats up in the sun, the soil heats up and begins to dehydrate.

Hope that helps.

Not sure if this might help or not but Miracle Grow has a brand of soil that is Moisture Control. IT's sort of like a time release soil.