If your garden has all day sun exposure, your landscape does not include irrigation, or there are water restriction concerns, consider a garden that focuses on drought-tolerant plants.
However, a perennial plant will require water to establish itself, only when they have well-established roots will they tolerate drought.
While many drought-tolerant plants are also tolerant of poor-to-average soils, soils that are high in organic matter will help plants both establish themselves and survive periods of drought. Spending efforts to improve soil conditions will improve the gardens performance, but most drought tolerant perennials prefer soils that are well-drained.
Mulches are a prime gardening technique to reduce water evaporation. Not only will mulch assist the water problem, it adds organic matter to the soils and reduces weeds.
Plants to consider include - artemisia, aster, coreopsis, dianthus, echinacea, hemerocallis (daylily), heuchera (full shade in southern gardens), phlox, rubus, rudbeckia, scabiosa, sedum.