Wheat fields north of U.S. Highway 2 east of Wilbur, Washington
A fairly large area of eastern Washington is treeless. This is of course because parts of eastern Washington have yearly rain fall well under 10 inches. Irrigation has turned some portions of the previously treeless land to crop land including stands of trees (orchards). But large swaths of eastern Washington is non irrigated wheat as pictured above. The wheat land has pushed into areas that have enough rain to support trees without irrigation. I have to remind myself not to equate dry land wheat with desert.
Patch of ponderosa pines near Wilbur, Washington
Tree covered areas are located along areas of Highway 2 when the ground gets rocky and is not suitable for crops. Trees also cover the steeper slopes of a few of the bluffs near Creston. A few miles north of Wilbur on the north slopes above the deep Columbia River valley the slope it is moist enough to support Douglas fir.
In a number of areas where there is enough water to support trees along the outer edge of the true desert in eastern Washington, there has been extensive tree planting such that there are far more trees today than a few decades ago. Hence, the appearance of the eastern Washington landscape is changing based on commercial value of wood, fire control, and public and private desire for areas with trees. For some reason the generations of farmers that own the land pictured above decided they liked having that patch of trees. Perhaps they valued the shade provided for a break during the hard work of harvest.