Darwinian Gardening -- Dealing with a Limited Plant Palette - Repeat What Works
Plant long-bloomers and plants with much seasonal interest: Nepeta racemosa 'Walker's Low', Euphorbia epithymoides (cushion spurge -- red fall color)
Use bulbs to stretch the season: Tulipa batalinii and Glaucium corniculatum; Crocus speciosus with California poppies, Dendranthema zawadskii 'Mary Stoker'
Plant tough shrubs with multi-seasonal interest: Cytisus purgans
Use grasses: Sporobolus heterolepis 'prairie dropseed'
Add self-sowing annuals and biennials: Eschscholzia californica California poppies with 'Walker's Low' nepeta, Yucca baccata, Onosma echioides, Achillea x 'Moonshine', Echium lusitanicum and Alyssum markgrafii with potted agaves and Crassula falcata