Director King Vidor's own ranch in Paso Robles, California was used as a filming location for the Nolan Ranch.
Warner Bros. bought the rights to the novel in 1945. The film was produced in early 1950 but not released until March 1951.
The Joshua Trees shown are native to the Southwest Mojave Desert. A member of the lily family, they are found in the high desert around Victorville, CA, one of the filming locations. UPDATE: recent studies have shown that the Joshua tree, yucca brevifolia, is actually part of the agave family.
Halfway through the film, Shelley and Liza are in "downtown" Victorville on D St. near the corner of 7th St. They are on US routes 66 and 91, while CA 18 continues straight ahead. It looks like none of the buildings exist anymore on that block. (Rexall drug store, etc.) There exists the Route 66 Museum behind them.
The terrain around the King Vidor ranch is quite different from that of the Tumble Moon establishment. That's because Vidor's beautiful mid-century spread was located in Pasa Robles, in the hills between the central California coast and the San Joaquin Valley, and not in the high desert around Victorville. The two locations are nearly 250 miles apart.