Dormancy

Dormancy is a period in a plant's life cycle when growth is temporarily stopped.
Note that the lists below include mainly genera, there are cases where a species within a genus has the opposite dormancy to the majority in that genus.
Also note that when some plants are grown outside of their native habitat, especially in the opposite hemisphere, they can change their dormancy habits.
This group is usually referred to as “summer growers.” They are dormant from November through February (June through September in the southern hemisphere). Many of these will also enter a rest period for a few weeks during the hottest part of the summer (called estivation). Genera fitting better in this category include:
Acer
Adenia
Adenium
Alluaudia
Aloidendron
Aloinopsis rubrolineata
Anemopsis
Aporocactus
Arbutus
Ariocarpus
Astrophytum
Austrocylindropuntia
Avonia quinaria
Aylostera
Beaucarnea
Brachystelma
Browningia
Bursera
Calibanus
Caputia
Caralluma
Cereus
Ceropegia
Chamaecereus
Cissus
Cleistocactus
Coleus
Copiapoa
Coryphanthas
Crassula (most)
Cuphear
Curio
Cussonia
Cyphostemma
Dasylirion
Deuterocohnia
Didieria
Dioon
Dioscorea (some)
Discocactus
Dorstenia (most)
Dracaena
Dyckia
Ebracteola
Echeveria
Echinoagave
Echinobivia
Echinocactus
Echinofossoluscactus
Echinopsis
Encephalartos
Epiphyllum
Eriosycepus
Erythrina
Erythrostemon
Espostoa
Euphorbia (most)
Ferocactus
Ficus (most)
Fockea
Frailea
Gasteraloe
Glottiphyllum (& Summer)
Graptopetalum (most)
Gymnocalycium
Haemanthus (& Summer)
Haworthia (& Summer)
Haworthiopsis
Hechtia
Helictotrichon
Hoodia
Huernia
Hylocereus
Ibervillea
Ipomoea
Jatropha
Kleinia (most)
Kroenleinia
Leuchtenbergia
Lithops (& Summer)
Lobivia
Mammillaria
Mangave
Matucana
Melocactus
Mestoklema
Monadenium
Monanthes
Monotropa
Moringa
Myrtillocactus
Neochilenia
Neoporteria
Nymphoides
Operculicarya
Opuntia
Oreocereus
Ornithogalum
Oroya
Pachycereus
Pachypodium
Pachyveria (& Summer)
Parodia
Pedilanthus
Pelargonium
Pelecyphora
Petopentia
Petrosedum
Pilosocereus
Plumeria
Pseudolithos
Pterodiscus
Puya
Raphionacme
Rebutia
Sedeveria
Sedum
Selenicereus
Sempervivum
Senecio (& Summer)
Sinningia
Soehrensia
Stangeria
Stapelia
Stapelianthus
Stenocactus
Stenocereus
Stetsonia
Sulcorebutia
Synadenium
Tephrocactus
Thelocactus
Tillandsia
Titanopsis (some)
Trichocaulon
Trichocereus
Trochomeria
Turbinicarpus
Uebelmannia
Uncarina
Verbena
Xerosicyos
Usually referred to as “winter growers” these genera are mostly dormant during the warmer months of May through August (November through February in the southern hemisphere). Their primary growth actually occurs during the autumn and spring while slowing considerably during winter. Genera fitting better in this category include:
Adromischus
Aeonium
Agave
Aichryson
Albuca
Aloe
Aloinopsis (most)
Anacampseros
Argyroderma
Astroloba
Avonia (most)
Baculellum
Bowiea
Brachychiton (dry season)
Bulbine
Caputia
Ceraria
Chasmanthe
Cheiridopsis
Conophytum
Cotyldeon
Crassula (some)
Curio
Dactylopsis
Dioscorea (some)
Dracaena
Dudleya
Euphorbia (some)
Faucaria
Fenestraria
Fouquieria (dry season)
Gasterhaworthia
Gasteria
Gibbaeum
Glottiphyllum (& Winter)
Graptopetalum (some)
Graptosedum
Graptoveria
Greenovia
Haemanthus (& Winter)
Haworthia (& Winter)
Kalanchoe (some)
Kleinia
Kumara
Lithops (& Winter)
Machairophyllum
Massonia
Mesembryanthemum
Monanthes
Neohenricia
Orbea (dry season)
Othonna
Pachycormus
Pachyphytum
Pachyveria (& Winter)
Pelargonium
Peperomia
Phyllobolus
Pilea
Pleiospilos
Portulacaria
Sansevieria
Sarcocaulon
Senecio (& Winter)
Sphalmanthus
Stomatium
Sulcorebutia rauschii
Talinum
Titanopsis (most)
Trichodiadema
Tylecodon