What trees do you grow in the desert zones 7 and 8?

For adaptation purposes I'm doing a little research about plants that can take my level of cold here in the Pacific Northwest but that can survive our dry summers. To that end, I'm wondering what trees do well for those of you in arid regions in USDA zone 7-8, or the equivalent. Bonus if it doesn't need irrigation after establishment

The dry summer is not much of a problem in most cases it is the damp foggy weather that tends to spread viruses and cankers among stone fruit.  If your dirt dries out in the summer then incorporating highly fungal compost and wood chips may help keep a saturated sponge into the dry months.   If you buy trees get them from a local nursery that is familiar with needed disease resistance. You can see pictures of what I am growing on the Qberry Farm page.

Hi Hans

Disease hasn't much of a problem for me. Even with thick mulching, I've lost trees to drought, including locally adapted ones and natives (this, in a loam soil in western Washington). I'm hoping to reduce or negate the need for irrigation

Is qberry farm's website the Facebook page? Thanks!

What time of year were the trees planted?  Did they have a winter to develop roots?  Have you tried starting from seed?
I have every thing from high sandy loam and gravel to white clay like Mt St Helens ash in my flood plain.   The discounted trees at the box store at the end of summer did great planted in the sandy loam in fall with just enough leaves to send some sugar to the roots before they fell.  My peach trees are seedlings from compost in my planters. I have to keep them in a high tunnel to prevent disease. Plums are unstoppable and Italian prunes in the sandy loam die back  after a few years but come back up from the roots which spread far out so I always have an abundance.  Green and red grapes compete with the blackberries for dominance.   You are welcome to come get some root stock in September  if you want to try them.

Yes, I've tried everything--fall planting included. It's also quite a bit drier inland with no summer fog, even in what is still western Oregon and Washington. I grew up near where you are and the added dew is definitely an advantage there

Anyway, dragging this thread back on track you seem to be asking about what kind of fruit bearing plants are already adapted to dry environments, but can survive the cold AND wet of our winters and springs in the PNW? Figs and pomegranates come to mind as being pretty easy go-to plants for arid climates. They don't mind the wet of the springs and falls, but do really well when pushed by dry summer conditions. Jujube is also very tolerant to dry summers, but can survive cold winters. Some people say they even thrive. Guava is borderline, but many of the Chilean varieties are able to survive the winters and do great in the dry hot summers.

If you're not against it, you could look at water holding crystals as a soil amendment? Deep mulching isn't going to really help after the water sponge has been depleted. What a lot of people don't understand about water and establishing trees is that water is prone to falling too deep into the soil where new roots can't reach and/or being too easily evaporated from the top layers where the new roots are currently trying to establish. Without something to maintain the water in that root layer while establishing you're gonna have a bad time.

A parallel thread on the same topic gave her location as between the mountain and Tacoma which means drying down slope winds from the east which do not get this far across the sound.  So I recommended that the understory native plants are important for maintaining the soil sponge even more than they are for me.  In my case planting fruit trees on the east side of evergreen trees protects them from sun scald by the setting summer sun.  The cultivated hedge of Himalaya blackberries protects the Loganberries from sun scaled the same way.  Only a seedling cherry has survived isolated in the field and it started in a scotch broom  infestation and the lower branches were head height when the scotch broom was removed.  So my observation is the soil for fruit trees in our climate needs  a supporting guild.