Questions about high-semidesert plants

Hi, all. I've got a young wild plum (_Prunus americana_) shrub that bloomed nicely last year but didn't set any fruit. Anyone know what might cause that? Any chance these trees aren't self-fertile?
Does anyone know how big the western sand cherry (_Prunus besseyi_) gets? One of my catalogs says 4 feet tall, one says 8 feet, and neither says anything about width. If it's more than 4 or 5 feet wide, I don't have room for it, unless I can prune it and still get flowers, fruit, and fall color.
Though I live in zone 6, supposedly, I've overwintered zone-7 plants by the south wall of my house. Now I'm considering some new tender plants for that spot. Anyone know the hardiness, heat tolerance, and drought tolerance, of _Salvia chamaedryoides_ and _Salvia_ x "Indigo Spires"? I'm finding conflicting information. This spot gets "more than full" sun, by the way--the altitude is over a mile and the only shade is for a few hours after sunrise.
And I have the same questions for the dwarf pomegranate "Nana". I like lots of colorful flowers and fruit--is that what I'll get? Will the fruit turn red or become edible in zone 7? (I'd love to give my Mexican neighbors homegrown pomegranates for their chiles en nogada on Mexican Independence Day, Sept. 16, but I'm not counting on it.)
Where I live, typical winter lows are in the 10s and 20s (F), typical summer highs are in the 90s, and there's often about 30 or 35 degrees between the high and low each day. I'm especially interested in experience from similar climates.
-- Jerry Friedman 360' N 1063' W, altitude 1700m (5600 feet), USDA zone 6
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