Whaas, I am thinking of my vacations to Phoenix, Vegas or Colorado. Darn cottonwoods were all over the place. Tons of conifers in dry Colorado.... Besides crab apples and Russian olives or whatever that invasive was I really did not see THAT many large shade trees....

The bur oak is probably the most drought-tolerant of the large "shade" trees. There are a few other deciduous trees that are more drought-resistant but they are smaller and/or not suitable for a Z5 climate.

Most any established oak or hard pine is drought resistant. Rock chestnut oaks are the best on the driest rock slopes in the Appalachians -- stunted, but healthy. Black, white & scarlet oaks too. Table Mnt pines survive on sun-scorched shale outcrops.

Honey locust here puts on new growth thru Sept no matter how hot/dry it is -- just slows down.

And the cottonwoods -- seen 'em in the NV desert. They're able to get roots way down in the sand (50' deep or more) to find underground water.

Gents, thanks for the feedback!

I'd consider the cottonwoods peasants. They are everywhere here as well. They are invasive if you ask me. My neighbor lets them grow and they are choking out his spruces, oaks and maples.

I'd love to roll with White and Scarlet oak but soil might be a bit too compacted and alkaline for both these plants. Quercus bicolor is another choice but they "can" struggle on 7.5 pH.

Q/.macrocarpa gets my vote, but Q.muehlenbergii would probably do well, too.
One of the thornless Osage Orange clones would probably also work - and you'd probably be the only person on the block with one!

Not a favorite of many but Quercus stellata is the poster child around here for your requirements.

Edit: I had no idea when I posted that that it's hardiness range was so far to the south Wisconsin. Not a good selection for you, sorry

This post was edited by j0nd03 on Sat, Jul 20, 13 at 20:00

Escarpment live oak trees rule central Texas when it comes to drought tolerant in the wild. I don't see many Bur oak trees or Texas Red oaks like that.

Escarpment Live oak has survived 3 winters in my zone 6 yard, not sure of zone 5a though. I would try it anyway, but mine is ULTRA slow growing. Mine is still about 14-16 inches tall after 4 summers. I thought it died, and I planted another Live oak hybrid near where it was and the new one is taller than the Q. Fusiformis, planted 3 + years ago, which came back from a sprout and pushed out about a foot of new branches. Try Quartz mountain Quercus Fusiformis if you try Live oak. Acorns of Burr oak are said to put down tap roots as long as 7 ft deep. I have one from acorns from Dax last fall, it is about 2 3/4 ft tall. It was the tallest of all the acorns I sowed. Will post pics soon.

Cupressus dupreziana in the Sahara.

Planted the acorn in the fall of 2012. Burr oak seed from Dax. {{gwi:383047}} It is still only July 21st. For drought tolerance I would plant acorns. Just my opinion, though.

Quartz mountain live oak are known to be -20F hardy. Zone 5 easy. But Burr oak acorns may be the way to go. Especially if you add tall tubes (3 ft) that should help the babies get some height. The depth of 7 ft taproot is of course not guaranteed, but is possible. The Quercus Fusiformis is a desert dweller though. If you have patience to see it grow SLOWLY it will surely be there growing about 6 inches annually. Maybe more once roots get going.

whaas, recommend chinkapin oak for alkaline soil. Pretty sure burr oak has some high pH tolerance too. Honeylocust, Kentucky coffeetree or osage orange (var Whiteshield is male, thornless & upright) don't mind higher pH soil either. All should be drought-tolerant when established.

Lucky, my Whiteshield osage orange now at 25' grows out of crushed limestone & is developing a vase-like form more like an Amer elm than a classic OO. Read somewhere that the males grow this way. Try cutting an OO branch is like cutting thru iron...

Appreciate all the addtional suggestions!

I forgot about Maclura pomifera Whiteshield. Might be a nice selection for another location.