Answer: Daylilies or iris are good choices. You might also consider the following low water use, low maintenance plants:
Shrubs include amur maple Acer ginnala, Japanese barberry Berberis thunbergii, quince Chaenomeles sp., smoketree Cotinus coggygria, Scotch broom Cytisus sp., Russian olive Elaeagnus angustifolia, witch hazel Hamamelis virginiana, privet Ligustrum sp., buckthorn Rhamnus sp., sumac Rhus sp., and yucca Yucca sp..
Groundcovers include yarrow Achillea sp., crown vetch Coronilla varia, sweet William Dianthus sp., daylilies Hemerocallis sp., cinquefoil Potentilla sp., lavender cotton Santolina chamaecyparissus, creeping phlox Phlox subulata, and St. Johnswort Hypericum sp..
Many of these plants come in a variety of flower and leaf colors, heights, thorniness, etc. depending on the species. Choose the species that will provide the features and ultimate size appropriate for the site you have chosen.
These plants will tolerate dry, poor soil conditions such as you'd find on a slope; however, as with any new planting, they will need to be watered until they are established.
Best wishes with your landscape!
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