Help with drought-tolerant plant?

I am in Oklahoma where it is VERY hot and dry. I planted basket of gold about a month ago and it keeps on dying. I am afraid to NOT water it because it has been 93-100 degrees the whole time with no rain. Am I over watering them? I don't give them LOTS of water, just a squirt at the base of the plant from a garden hose early in the morning. Help...I'm trying to plant gardens for my Mom that are no/low maintenance since the gardener in the family, my Dad, ped away at Christmas. Thanks!