Photo by Mia Ingolia. Sedum palmeri The Southwest USA and Mexican Collections complement each other to feature a continuum of plants native to the cordilleran region of the summer-rainfall areas of the North American West as far south as Guatemala. A grove of Rocky Mountain big-tooth maples and Arizonan pines grow next to Mexican pines and cypresses. Along the edge of the creek, the graceful forms of Montezuma cypresses and Guatemalan walnuts shade the water. Both native species and horticultural selections of salvias and Texas rangers (Leucophyllum) add brilliant reds, corals, and blues to the collection. Some massive, gnarled valley oaks, native to the site, provide shade for visitors along this south-facing collection.