Drought tolerance
(Keep in mind that these ratings are oriented towards climate with rainfall distributed throughout the year and average humidity levels above 40% RH.
Unless a plant is noted as particularly well-adapted to semi-arid regions, one should expect that the plant will be less drought tolerant than listed in such areas.)

High drought tolerance
Low drought tolerance
Acacia auriculiformis
  Earleaf Acacia
Acacia baileyana
  Cootamundra Wattle; Golden Mimosa
Acacia choriophylla
  Thornless Acacia
Acacia farnesiana
  Sweet Acacia
Acacia latifolia
  Bush Acacia
Acacia nilotica
  Gum-arabic Tree; Stuntwood; Babul
Acacia pinetorum
  Pineland Acacia
Acanthopanax sieboldianus
  Fiveleaf Aralia
Acer buergeranum
  Trident Maple
Acer campestre
  Hedge Maple
Acer truncatum
  Purpleblow Maple; Shantung Maple
Achillea spp.
  Yarrow
Acrocomia totai
  Grugru Palm
Adansonia digitata
  Baobab
Adenium obesum
  Desert Rose
Aechmea bracteata
  Vase Bromeliad
Aechmea chantinii
  Amazonian Zebra Plant
Aechmea fasciata
  Silver Vase
Aechmea fulgens
  Coral Berry Vase
Aechmea mexicana
  Mexican Vase
Agave americana
  Century Plant
Agave angustifolia
  Caribbean Agave
Agave atrovirens
  Maguey Del Cumbre; Pulque Agave
Agave attenuata
  Spineless Century Plant
Agave desmettiana
  Dwarf Century Plant
Agave neglecta
  Wild Century Plant
Akebia quinata
  Fiveleaf Akebia
Albizia julibrissin
  Mimosa; Silk Tree
Albizia lebbeck
  Mother In Law's Tongue; Lebbek Tree
Aleurites fordii
  Tung Oil Tree; China Wood-oil Tree
Aleurites moluccana
  Candlenut
Allagoptera arenaria
  Seashore Palm
Aloe arborescens
  Candelabra Aloe; Candelabra Plant
Aloe barbadensis
  Barbados Aloe; Mediterranean Aloe
Aloe saponaria
  Soap Aloe
Aloe thraskii
  Thrask Aloe
Alternanthera ficoidea
  Joseph's-coat
Alyogyne heugelii
  Blue Hibiscus
Amaranthus tricolor
  Joseph's Coat; Fountain Plant; Tampala; Prince's Feather
Amelanchier canadensis
  Shadebush; Junebush; Shadeblow Serviceberry
Amelanchier X grandiflora
  Apple Serviceberry
Amphitecna latifolia
  Black Calabash
Amyris elemifera
  Torchwood
Ananas comosus
  Pineapple
Angadenia berterii
  Pineland Allamanda
Antigonon leptopus
  Coral Vine
Aphanostephus skirrhobasis
  Lazy Daisy
Aptenia cordifolia
  Baby Sun Rose
Araucaria heterophylla
  Norfolk Island Pine
Arbutus unedo
  Strawberry Tree; Cane Apple
Archontophoenix alexandrae
  Alexandra Palm; King Alexander Palm
Archontophoenix cunninghamiana
  Piccabeen Palm
Asclepias tuberosa
  Butterfly Weed
Asparagus densiflorus
  Asparagus Fern
Asparagus falcatus
  Sicklethorn Vine
Asparagus setaceus
  Asparagus Fern
Asystasia gangetica
  Ganges Primrose
Azadirachta indica
  Neem Tree
Baccharis halimifolia
  Groundsel Bush; Salt Bush
Bambusa glaucescens
  Hedge Bamboo
Baptisia spp.
  False Indigo
Bauhinia blakeana
  Hong Kong Orchid Tree
Bauhinia monandra
  Butterfly Flower
Bauhinia punctata
  Red Bauhinia
Bauhinia purpurea
  Fall Orchid Tree
Bauhinia variegata
  Orchid Tree; Buddhist Bauhinia
Beaucarnea gracilis
  Bottle Ponytail
Beaucarnea recurvata
  Ponytail; Elephant-foot Tree
Bismarckia nobilis
  Bismarck Palm
Blighia sapida
  Akee; Vegetable Brain
Borassus flabellifer
  Palmyra Palm; Lontar Palm
Borrichia arborescens
  Silver Sea Oxeye
Bougainvillea glabra
  Lesser Bougainvillea; Paper Flower
Bougainvillea spectabilis
  Bougainvillea
Bourreria succulenta var. revoluta
  Strongbark
Brachychiton acerifolius
  Flame Bottle Tree
Brachychiton discolor
  Scrub Bottle Tree
Brahea armata
  Blue Hesper Palm
Brahea edulis
  Guadalupe Palm
Brassaia actinophylla
  Schefflera; Umbrella Tree; Octopus Tree
Broussonetia papyrifera
  Paper Mulberry
Brya ebenus
  Jamaican Rain Tree; West Indian Ebony
Bucida buceras
  Black Olive
Bucida spinosa
  Spiny Black Olive
Bulnesia arborea
  Bulnesia
Bumelia reclinata
  Slender Buckthorn
Bumelia tenax
  Tough Buckhorn
Bursera simaruba
  Gumbo Limbo; Tourist Tree
Butia capitata
  Pindo Palm; Jelly Palm
Byrsonima lucida
  Locustberry
Caesalpinia pulcherrima
  Dwarf Poinciana
Calliandra haematocephala
  Red Powderpuff
Calliandra surinamensis
  Pink Powderpuff
Callicarpa americana
  American Beautyberry; Beautybush
Callisia fragrans
  Fragrant Callisia
Calyptranthes pallens
  Spicewood; Pale Lid Flower
Campsis grandiflora
  Chinese Trumpetcreeper
Campsis radicans
  Trumpet Vine; Trumpet Creeper
Canavallia maritima
  Beach Bean
Canella winterana
  Wild Cinnamon
Capparis cynophallophora
  Jamaican Caper
Capparis flexuosa
  Bay-leaved Caper Tree
Carissa grandiflora
  Natal Plum
Carissa macrocarpa
  Natal Plum
Carpobrotus spp.
  Hottentot Fig
Carya floridana
  Scrub Hickory
Carya glabra
  Pignut Hickory
Carya illinoinensis
  Pecan
Casasia clusiifolia
  Seven-year Apple
Cassia bahamensis
  Bahama Cassia
Casuarina equisetifolia
  Australian Pine Tree
Catharanthus roseus
  Periwinkle
Cattleya spp.
  Cattleya Orchid
Cedrus libani
  Cedar of Lebanon
Ceiba aesculifolia
Ceiba pentandra
  Silk-cotton Tree; Kapok Tree
Celtis laevigata
  Sugarberry; Hackberry
Centranthus ruber
  Jupiter's Beard; Red Valerian
Ceratiola ericoides
  Rosemary
Ceratonia siliqua
  Carob; St. John's Bread
Cercis canadensis
  Redbud; Eastern Redbud
Cercis chinensis
  Chinese Redbud
Cercis siliquastrum
  Judas Tree; Redbud
Cereus peruvianus
  Hedge Cactus; Peruvian Apple Cactus
Chamaerops humilis
  European Fan Palm
Chiococca alba
  Snowberry
Chiococca pinetorum
  Pineland Snowberry
Chorisia insignis
  White Floss-silk Tree;
Chorisia speciosa
  Floss-silk Tree; Silk-floss Tree
Chrysalidocarpus cabadae
  Cabada Palm
Chrysalidocarpus lutescens
  Areca Palm; Butterfly Palm
Chrysanthemum leucanthemum
  Oxeye Daisy
Chrysophyllum oliviforme
  Satin Leaf
Cissus incisa
  Marine Ivy
Citharexylum fruticosum
  Fiddlewood
Cladrastis lutea
  Yellow Wood
Clematis hybrida
  Leather Flower; Large Flowered Clematis
Clusia rosea
  Pitch Apple; Autograph Tree
Coccoloba diversifolia
  Pigeon Plum
Coccoloba uvifera
  Sea Grape
Coccothrinax alta
  Silver Palm; Fan Palm
Coccothrinax argentata
  Silver Palm
Coccothrinax crinita
  Old Man Palm
Coccothrinax miraguama
  Miraguama Palm
Cochlospermum vitifolium
  Buttercup Tree
Cocos nucifera
  Coconut Palm; Malayan Palm
Codiaeum variegatum var. pictum
  Croton
Colubrina arborescens
  Coffee Colubrina
Conocarpus erectus
  Buttonwood
Conocarpus erectus var. sericeus
  Silver Buttonwood
Conradina grandiflora
  Conradina
Copernicia baileyana
  Bailey Copernicia Palm
Copernicia hospita
  Hospita Copernicia
Copernicia macroglossa
  Cuban Petticoat Palm
Cordia boissieri
  Texas Wild Olive; White Geiger
Cordia sebestena
  Geiger Tree
Cordyline australis
  Giant Dracaena; Cabbage Tree
Cordyline rubra `Bruantii'
  Bruantii Dracaena
Cortaderia rudiuscula
  Pampas Grass
Cortaderia selloana
  Pampas Grass
Corylus colurna
  Turkish Filbert
Corypha elata
  Gebang Palm
Cotinus coggyria
  Smoketree; Smokebush
Cotoneaster horizontalis
  Rockspray Cotoneaster
Crassula argentea
  Jade Plant
Crassula obliqua
  Jade Plant
Crataegus spp.
  Hawthorns
Crescentia alata
  Mexican Calabash
Crossopetalum ilicifolium
  Quail Berry; Christmasberry
Cryptanthus spp.
  Earth Star
Cryptocereus anthonyanus
  Anthony's Rick-rack; Zigzag Cactus
Cryptostegia grandiflora
  Palay Rubber Vine; Purple Allamanda
Cryptostegia madagascariensis
  Madagascar Rubber Vine
Cupressus arizonica
  Arizona Cypress
Cupressus lusitanica
  Portuguese Cypress; Mexican Cypress
Cupressus macrocarpa `Golden Pillar'
  Golden Pillar Cypress
Cycas circinalis
  Queen Sago
Cycas revoluta
  King Sago
Cycas taiwaniana
  Prince Sago
Cydista aequinoctialis
  Garlic Vine
Dalbergia ecastophyllum
  Coin Vine
Datura metel
  Trumpet Flower
Delonix regia
  Royal Poinciana; Flame Tree; Flamboyant Tree
Dendrobium nobile
  Nobile Dendrobium
Dendrobium spp.
  Dendrobium Orchid
Dendrocalamus strictus
  Male Bamboo
Dioon edule
  Chamal
Dioon spinulosum
  Spiny Dioon
Dipholis salicifolia
  Willow-leaved Bustic
Dodanaea viscosa
  Varnish Leaf
Dracaena draco
  Dragon Tree
Dracaena marginata
  Red-edged Dracaena
Dracaena reflexa
  Reflexed Dracaena
Dracaena sanderiana
  Ribbon Plant
Dracaena thalioides
  Lance Dracaena
Drypetes lateriflora
  Guiana Plum
Duranta