Answer: If I may, please allow me to recommend a great book for your daughter's situation. It's called "Xeriscape Gardening: Water Conservation for the American Landscape" by Connie Ellefson (Macmillan, 1992). It has lots of information about dry-climate gardening. Some perennials include: Coreopsis, Purple Coneflower (Echinacea purpurea), Black-eyed Susan (Rudbeckia), Russian Sage (Perovskia 'Filigran'), Autumn Joy Sedum (Sedum Spectabile 'Autumn Joy'), and Ballerina Hardy Geranium (Geranium cinereum 'Ballerina'). She will need to keep them watered until they establish themselves - water them about once per week throughout the summer and fall (unless there is adequate rainfall). After that, they should be doing well enough to forge ahead on their own.
Some annuals include: Portulaca - they thrive despite drought - these little succulents are built for the challenge, and flower beautifully on neglect. They're low growing, so you can back them up with tall marigolds, tithonia, sunflowers, zinnias. Thunbergia and nasturtiums are also good for containers in dry areas. Deadhead (remove spent blooms) often to promote more flowering.
Here are some trees: Gray Birch, Hackberry, Junipers, Golden Rain Tree, Osage Orange, Locust, Sassafrass.
Shrubs: Japanese Barberry, Quince, Smoketree, Broom, Russian Olive, Witch Hazel, Privet, Buckthorn, Sumac, Yucca.
Remind her that all of these will need a regular supply of water while they are establishing themselves. Especially important the first season, also important (though not as much) the second. After that, they should be fine on their own.
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