If you want a carefree garden that you do not have to water you need to plant the stress-tolerants of your plant community and make them happy. If you do not mind pruning the flower heads and dead foliage each year, use the Circumventers of your plant community. If you want a lot of flowers and are willing to turn your garden over every 3-6 months, use the ruderals of the world. If your site is very cold, hot, dry, windy or infertile or you have limited time, find a stress-tolerant plant. The western plants that are native in the mountains where they get summer thunder showers can be brought east as long as you do not fertilize and do not overwater.
Most western natives grow poorly under a garden regime where the ruderals are quite happy.
Most eastern natives would not do well under a garden regime where the western drought tolerants were thriving. The eastern plants can be brought west with regular summer water. For years, we treated the ruderals of our vegetable garden as we did our CA natives. We found that the fruit trees were Circumventers, could become very drought tolerant and needed little or no fertilizer. When our customers treated drought tolerant plants like they treated vegetables or garden flowers, the plants grew very quickly into large, lush specimens and promptly died.