I have often marveled at fruit trees growing wild in dry North Central Washington. I associate fruit trees with irrigation and lushness. They may need irrigation to be fruitful, but fruit trees seem to be able to survive with just the water that falls out of the sky. I have seen apple, pear, plum, and apricot trees growing in very dry places. I have seen cherry trees in creek bottoms right next to sagebrush. Normally, what one sees, is abandoned trees at old homestead and ranch sites.
The most striking example of fruit trees I have come across, is the apricots at the mouth of Toat's Coulee in Okanogan County, west of Loomis. These trees are growing on a rocky slope among sagebrush and bitterbrush. There is no indication that there ever could have been irrigation. The trees are fending for themselves. Besides the larger apricot trees I found numerous small trees, that must have grown from pits spread by animals.
I recently learned from Peter Valaas, a fourth generation North Central Washington resident, that back in the day there was such a thing as "dryland apricot farming". Trees were planted but not irrigated. So, the original trees in Toat's Coulee may have been planted long ago, but they are clearly spreading, slowly.
Much has been said about non-native species taking over wild areas and wreaking havoc- Cheatgrass, carp, starlings, and knapweed being case in point. However, I will say that occasionally I come across non-native plants, particularly trees, that in my opinion add to biological diversity and the richness of life. If apricot trees keep on spreading into our shrub steppe areas, I don't think it will be a bad thing. The latin name for apricots is Prunus armeniaca. It got that name because it is thought to be native to Armenia. Weather-on-line describes the climate of Armenia as "....highland continental, dry with four seasons....." Summer can be quite hot and winters cold. Sound familiar?