Arizona Soil Issues? - Plants Won't Grow
I live in Tucson, AZ and purchased a house a year ago. The backyard was completely bare. I have since added some plant life, but have had issues. Plants will not grow. They will flower. They will, generally, stay green. But they will not grow.
Facts about the soil:
Highly Alkaline (8.2-8.5 pH range)
rocky, with slight caliche issues (I break it up with a drill prior to planting)
sandy, with small amounts of clay
In the year that I have lived in this house, I have planted the following:
six oleanders (the same height as when I planted them a year ago, about 1.5 feet);
Two crape myrtles (one died, the other has grown about 4 inches; starting height about 1.5 feet);
seven bougainvillea (died to the roots during winter, began leafing back out in February from the crown. The longest shoot is about 8 inches but most are 3-4 inches. Plants are healthy, just will not grow out.);
two more crape myrtles (planted two months ago, blooms beautifully and are leafed out, but are now growing outward.)
12 butterfly bush (buddleia davidii) (died within a month of being put in the ground.)
I believe the house was built on a lot that previously burned down because the only old tree in the yard has severe burns on it and is growing back from the burn sites. I do not know if this could have effected the soil. Everyone I've talked to, including Lowes, has told me that the bougainvillea, even if it died to the crown, should have been six feet tall by now. The new crape myrtles are beautiful, but still twig like and can barely stand on their own. They are not branching out. The buddleia, which I bought from green things, died, all twelve of them, literally within a month.
There is something in the soil plants either don't like or something not in the soil that plants need. I cannot figure out how to get them to grow outward, vine out, branch out, whatever. I have applied osmocote, I have tried miracle grow, etc.
I amend the soil, while planting, with composted cow manure. I do not mulch because the sandy/clay mixture tends to cake up and suffocate the roots, so if it's mulched you cannot see that happening beneath the mulch to thin the muck prior to that happening.
Is there anything I should top on the soil to make things grow out? The crape myrtles are beautiful, but I don't want blooming tooth picks. The other crape myrtle has been in the ground for a year and has grown four inches. They're all fast-growing varieties *pink valous, red dynamite, and muscogee). The bougainvillea, again, should be long as hell by now. The longest shoot is eight inches...
Do I need to add iron to my soil? What is missing here?