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:
Adenia
Adenium
Alluaudia
Aloinopsis rubrolineata
Beaucarnia
Brachystelma
Bursera
Calibanus
Ceropegia
Cissus
Cyphostemma
Didieria
Dioon
Dorstenia
Dyckia
Echeveria
Encephalartos
Euphorbia
Ficus
Fockea
Hechtia
Huernia
Hylocereus
Ibervillea
Ipomoea
Jatropha
Monadenium
Moringa
Operculicarya
Orbea
Pachypodium
Pedilanthus
Plumeria
Pseudolithos
Pterodiscus
Puya
Raphionacme
Selenicereus
Sempervivum
Sinningia
Stangeria
Stapelia
Stapelianthus
Synadenium
Tillandsia
Titanopsis
Trichocaulon
Trichodiadema
Uncarina
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
Aloe
Anacampseros
Astroloba
Avonia
Bowiea
Bulbine
Caputia
Ceraria
Conophytum
Cotyldeon
Crassula
Curio
Dactylopsis
Dracaena
Dudleya
Fenestraria
Fouquieria
Gasteria
Gibbaeum
Graptopetalum
Graptosedum
Graptoveria
Greenovia
Haemanthus
Haworthia
Haworthiopsis
Kalanchoe
Kleinia
Kumara
Lithops
Monanthes
Neohenricia
Othonna
Pachycormus
Pachyphytum
Pachyveria
Pelargonium
Peperomia
Pilea
Portulacaria
Sansevieria
Sarcocaulon
Sedeveria
Sedum
Senecio
Sphalmanthus (Phyllobolus)
Stomatium
Sulcorebutia rauschii
Talinum
Tylecodon