Reasonably Drought Tolerant Plants

Here is a list of plants, fairly easily available & reasonably drought tolerant to be used to choose new plants for the ornamental border in the future.

Reasonably Drought Tolerant Plants for Sun

Shrubs
Arctostaphylos columbiana (Hairy Manzanita) Arctostaphylos densiflora (Vine Hill Manzanita) Arctostaphylos ‘Sunset’ & others
Berberis thunbergii 'Crimson Pygmy', Berberis thunbergii 'Helmond Pillar', Berberis thunbergii 'Rose Glow', Berberis thunbergii 'Royal Cloak' (Japanese Barberry) & others
Calluna vulgaris (Heather)
Caryopteris x clandonensis (Bluebeard)
Daboecia cantabrica (Irish Heath)
Erica arborea 'Estrella Gold', Erica australis, Erica carnea, Erica x darleyensis (Heath) & others
Hebe buxifolia, Hebe ochracea, Hebe 'Red Edge', Hebe topiaria, Hebe ‘Western Hills’ & others
Hypericum androsaemum 'Albury Purple', Hypericum 'Hidcote' (St John's Wort) & others
Lithocarpus densiflorus var. echinoides (Dwarf Tanoak)
Myrtus communis (Common Myrtle)
Olearia x haastii, Olearia x mollis
Phlomis fruticosa (Jerusalem Sage) & other species
Potentilla fruticosa (Cinquefoil)
Rosa rugosa (Sea Tomato)
Senecio monroi (name changed to Brachyglottis)
Yucca filamentosa ‘Color Guard’, Yucca filamentosa ‘Bright Edge’ (Yucca)

Perennials
Achillea millefolium (Yarrow)
Allium (Ornamental Onion) many species
Armeria maritima (Thrift)
Aster (Michaelmas Daisy)
Baptisia australis (False Indigo)
Camassia leichtlinii, Camassia quamash (Camas)
Crocus many species
Echinops ritro (Globe Thistle)
Echinacea purpurea (Purple Coneflower)
Erigeron glaucus (Beach Aster) Erigeron karvinskianus (Santa Barbara Daisy) Erigeron speciosus (Showy Fleabane) & others
Eryngium amethystinum, Eryngium bourgatii, Eryngium variifolium (Sea Holly) & others
Euphorbia characias, Euphorbia x martinii, Euphorbia rigida (Spurge): & others
Festuca glauca (Blue Fescue)
Geranium cantabrigiense, Geranium sanguineum (Cranesbill) & others
Helianthemum nummularium (Sunrose)
Helleborus argutifolius (Corsican Hellebore)
Hemerocallis (Daylily)
Hyacinthus orientalis (Hyacinth)
Iris douglasiana (Douglas Iris)
Kniphofia (Torch Lily)
Lobelia tupa (Tupa)
Ornithogalum umbellatum (Star of Bethlehem)
Paeonia (Peony)
Panicum virgatum (Switchgrass)
Pennisetum setaceum (Fountain Grass)
Phlomis russeliana (Jerusalem Sage)
Romneya coulteri (Matilija Poppy)
Salvia (Sage)
Scilla peruviana (Giant Squill)
Tulipa batalinii, Tulipa turkestanica (Tulip) & other species
Scrophularia macrantha
Sedum 'Autumn Joy', Sedum 'Matrona', Sedum 'Vera Jameson' (Stonecrop) & others

Groundcovers

Arctostaphylos x media (A columbiana x A uva-ursi) Arctostaphylos nevadensis (Pinemat Manzanita) Arctostaphylos uva-ursi (Kinnikinnick) & other species
Aubrieta deltoidea (Rock Cress)
Aurinia saxatilis (Basket of Gold)
Campanula carpatica (Carpathian Harebell)
Ceanothus gloriosus (Point Reyes Ceanothus) Ceanothus griseus var. horizontalis (Carmel Creeper)
Hebe glaucophylla, Hebe x pimeleoides, Hebe pinguifolia 'Pagei' (Hebe)
Hypericum cerastioides (St John’s Wort)
Juniperus conferta (Shore Juniper) Juniperus procumbens (Japanese Garden Juniper) Juniperus squamata 'Blue Carpet'
Lithodora diffusa (Lithodora)
Penstemon pinifolius (Pineleaf Beardtongue)
Rosmarinus officinalis ‘Prostratus’ (Trailing Rosemary)
Sedum oreganum, Sedum reflexum 'Angelina', Sedum spathulifolium 'Cape Blanco', Sedum spurium (Stonecrop) & others
Veronica pectinata (Woolly Speedwell) Veronica prostrata (Harebell Speedwell)

Reasonably Drought Tolerant Plants for Shade or Part Shade
Shrubs
Camellia japonica, Camellia sasanqua
Chamaecyparis obtusa ‘Nana Gracilis’ (Dwarf Hinoki Cypress)
Choisya ternata 'Aztec Pearl', Choisya ternata 'Sundance' (Mexican Orange)
Fatshedera lizei
Fatsia japonica
Hydrangea quercifolia (Oakleaf Hydrangea)
Ilex cornuta (Chinese Holly)
Kalmia latifolia (Mountain Laurel)

Mahonia repens (Creeping Oregon Grape)
Nandina domestica (Heavenly Bamboo)
Osmanthus heterophyllus 'Goshiki', Osmanthus heterophyllus 'Ogon'  
Pieris japonica (Lily of the Valley Shrub)
Ribes sanguineum (Flowering Currant)
Vaccinium ovatum (Evergreen Huckleberry)
Viburnum davidii (David's Viburnum)
Rhaphiolepis umbellata, Rhaphiolepis umbellata ‘Minor’ (Yeddo Hawthorne)

Perennials
Achlys triphylla (Vanilla Leaf)
Anemone x hybrida (Japanese Anemone)
Bergenia (Elephant Ears)
Campanula latifolia (Bellflower)
Dicentra formosa (Bleeding Heart)
Digitalis purpurea (Foxglove)
Epimedium (Barrenwort)
Euphorbia amygdaloides ‘Purpurea’ (Woodspurge) Euphorbia x martinii
Geranium himalayense, Geranium 'Johnson's Blue', Geranium macrorrhizum, Geranium phaeum, Geranium pratense
Helleborus x hybridus, Helleborus lividus, Helleborus x sternii
Hosta sieboldiana
Liriope muscari (Lily Turf)
Luzula sylvatica (Woodrush)
Narcissus (Daffodil)
Polygonatum odoratum (Solomon’s Seal)
Polystichum munitum (Sword Fern)
Smilacina racemosa (False Solomon’s Seal)
Tellima grandiflora (Fringe Cup)
Tolmiea menziesii (Piggyback Plant)

Groundcovers
Campanula poscharskyana (Serbian Bellflower)
Fragaria vesca (Woodland Strawberry)
Maianthemum dilatatum (False Lily of the Valley)
Microbiota decussata (Carpet Cypress)
Sedum forsterianum, Sedum spathulifolium