When the heat of summer arrives, tough perennials will keep the garden in bloom. While there are few plants that can live without any water at all, drought tolerant types will withstand periodic dry spells, once established. Dianthus offers dainty fringed flowers while the daisy like blooms of Blanket Flower are bright and cheery. Gaura and Stonecrop are both low maintenance choices. Low growing Thyme thrives on dry heat and Veronica will provide colorful flower spikes.