While Zen gardens in Japan are typically very open, I find them to be a great solution to those difficult to plant, heavily shaded areas of the landscape.  In fact, many of the plants utilized in karesansui gardens, such as azaleas, mondo, and ferns require shade in Oklahoma.  Of course, we cannot grow that amazing moss.  Outside of Japan, many karesansui gardens substitute plants that are representative of the forms found in a traditional Japanese dry garden, but are better adapted to the local climate.  We could replace moss, with a groundcover that is more tolerant of Oklahoma’s heat, such as wire vine (Muehlenbeckia axillaris) or blue star creeper (Laurentia fluviatilis).  For a sunny Zen garden try a low-growing sedum or creeping thyme in place of moss. 

Without a speck of dust being raised,
the mountains tower up,
without a single drop falling,
the streams plunge into the valley.

~ Muso Soseki ~