Succulent plant

Not to be confused with cactus; botanically cacti are succulents but not all succulents are cacti.

Succulent plants, such as this Aloe, store water in their fleshy leaves

In botany, succulent plants, also known as succulents or sometimes fat plants, are plants having some parts that are more than normally thickened and fleshy, usually to retain water in arid climates or soil conditions. Succulent plants may store water in various structures, such as leaves and stems. Some definitions also include roots, so that geophytes that survive unfavourable periods by dying back to underground storage organs may be regarded as succulents. In horticultural use, the term "succulent" is often used in a way which excludes plants that botanists would regard as succulents, such as cacti. Succulents are grown as ornamental plants because of their striking and unusual appearance.

Definition

There are a number of somewhat different definitions of the term succulent. One difference lies in whether or not roots are included in the parts of a plant which make it a succulent. Some authors include roots, as in the definition "plants in which the leaves, stem or roots have become more than usually fleshy by the development of water-storing tissue." Others exclude roots, as in the definition "a plant with thick, fleshy and swollen stems and/or leaves, adapted to dry environments". This difference affects the relationship between succulents and "geophytes" – plants that survive unfavourable seasons as a resting bud on an underground organ. These underground organs, such as bulbs, corms and tubers, are often fleshy with water-storing tissues. Thus if roots are included in the definition, many geophytes would be classed as succulents.

Plants adapted to living in dry environments are termed xerophytes; thus succulents are often xerophytes. However, not all xerophytes are succulents, since there are other ways of adapting to a shortage of water, e.g. by developing small leaves which may roll up or having leathery rather than succulent leaves. Nor are all succulents xerophytes, since plants like Crassula helmsii are both succulent and aquatic.

Those who grow succulents as a hobby use the term in a different way to botanists. In horticultural use, the term succulent regularly excludes cacti. For example, Jacobsen's three volume Handbook of Succulent Plants does not cover cacti, and "cacti and succulents" is the title or part of the title of many books covering the cultivation of these plants. However, in botanical terminology, cacti are succulents. Horticulturalists may also exclude other groups of plants, e.g. bromeliads. A practical, but unscientific, horticultural definition is "a succulent plant is any desert plant that a succulent plant collector wishes to grow". Such plants less often include geophytes (in which the swollen storage organ is wholly underground) but do include plants with a caudex, which is a swollen above-ground organ at soil level, formed from a stem, a root or both.

A further difficulty is that plants are not either succulent or non-succulent. In many genera and families there is a continuous sequence from plants with thin leaves and normal stems to those with very clearly thickened and fleshy leaves or stems, so that deciding what is a succulent is often arbitrary. Different sources may classify the same plant differently.

Appearance

A collection of succulent plants, including cacti

The storage of water often gives succulent plants a more swollen or fleshy appearance than other plants, a characteristic known as succulence. In addition to succulence, succulent plants variously have other water-saving features. These may include:

• Crassulacean acid metabolism (CAM) to minimize water loss
• absent, reduced, or cylindrical-to-spherical leaves
• reduction in the number of stomata
• stems as the main site of photosynthesis, rather than leaves
• compact, reduced, cushion-like, columnar, or spherical growth form
• ribs enabling rapid increases in plant volume and decreasing surface area exposed to the sun
• waxy, hairy, or spiny outer surface to create a humid micro-habitat around the plant, which reduces air movement near the surface of the plant, and thereby reduces water loss and creates shade
• roots very near the surface of the soil, so they are able to take up moisture from very small showers or even from heavy dew
• ability to remain plump and full of water even with high internal temperatures (e.g. 52 °C or 126 °F)
• very impervious outer cuticle (skin)
• mucilaginous substances, which retain water abundantly

Habitat

Many succulents come from the dry areas of the tropics and subtropics, such as steppes, semi-desert, and desert. High temperatures and low precipitation force plants to collect and store water to survive long dry periods. Succulents may occasionally occur as epiphytes - "air plants" - as they have limited or no contact with the ground, and are dependent on their ability to store water and gain nutrients by other means; this niche is seen in Tillandsia. Succulents also occur as inhabitants of sea coasts and dry lakes, which are exposed to high levels of dissolved minerals that are deadly to many other plant species.

Evolution

The best-known succulents are cacti (family: Cactaceae). Virtually all cacti are succulents, but not all succulents are cacti. A unique feature of cacti is the possession of areoles, structures from which spines and flowers are produced.

To differentiate between these two basic types that seem so similar, but that are unrelated succulent plants, use of the terms, cactus or cacti, only should be used to describe succulents in the cactus family. Popular collection of these types of plants has led to many Old World plants becoming established in the wild in the New World, and vice versa.

Families and genera

Apocynaceae: Pachypodium lealii, stem succulent

Xanthorrhoeaceae: Haworthia arachnoidea, leaf succulent

Cactaceae: Rebutia muscula, stem succulent

Crassulaceae: Crassula ovata, stem and leaf succulent

Euphorbiaceae: Euphorbia obesa ssp. symmetrica, stem succulent

Cylindropuntia imbricata: stem, woody succulent

Malvaceae: Adansonia digitata, stem succulent

Moringaceae: Moringa ovalifolia, stem succulent

Asparagaceae: Beaucarnea recurvata, stem succulent

Asparagaceae: Dracaena draco, stem succulent

Euphorbia resinifera

Plant families and genera in which succulent species occur are listed below.

Order Alismatales

• Araceae: Zamioculcas

Order Apiales

• Apiaceae: Steganotaenia

• Araliaceae: Cussonia

Order Asparagales

• Amaryllidaceae (geophytes): Ammocharis, Apodolirion, Boophone, Brunsvigia, Crinum, Crossyne, Cryptostephanus, Cyrtanthus, Gethyllis, Habranthus, Haemanthus, Hessea, Nerine, Pancratium, Rauhia, Scadoxus, Strumaria, Zephyranthes,

• Asparagaceae
  • subfamily Agavoideae: Agave, Beschorneria, Chlorophytum, Furcraea, Hesperaloe, Hesperoyucca, Yucca
  • subfamily Asparagoideae: Asparagus
  • subfamily Lomandroideae: Cordyline,
  • subfamily Nolinoideae: Beaucarnea, Calibanus, Dasylirion, Dracaena, Nolina, Sansevieria, Eriospermum
  • subfamily Scilloideae: Albuca, Bowiea, Daubenya, Dipcadi, Drimia, Drimiopsis, Eucomis, Hyacinthus, Lachenalia, Ledebouria, Litanthus, Massonia, Merwilla, Namophila, Ornithogalum, Pseudogaltonia, Pseudoprospero, Resnova, Schizobasis, Schizocarphus, Spetaea, Veltheimia

• Doryanthaceae: Doryanthes

• Hypoxidaceae (geophytes): Empodium, Hypoxis, Pauridia, Saniella, Spiloxene

• Iridaceae (geophytes): Babiana, Chasmanthe, Crocosmia, Devia, Dierama, Dietes, Duthiastrum, Ferraria, Freesia, Geissorhiza, Gladiolus, Hesperantha, Ixia, Lapeirousia, Melasphaerula, Micranthus, Moraea, Pillansia, Radinosiphon, Romulea, Sparaxis, Syringodea, Thereianthus, Tritonia, Tritoniopsis, Watsonia, Xenoscapa

• Orchidaceae (succulents) Acampe, Aerangis, Ansellia, Bolusiella, Bulbophyllum, Calanthe, Cyrtorchis, Oberonia, Polystachya, Tridactyle, Vanilla

(succulent geophytes) Eulophia, Liparis, Oeceoclades

(geophytes) Acroliphia, Bartholina, Bonatea, Brachycorythis, Brownleea, Centrostigma, Ceratandra, Corycium, Cynorkis, Didymoplexis, Disa, Disperis, Dracomonticola, Eulophia, Evotella, Gastrodia, Habernaria, Holothrix, Huttonaea, Neobolusia, Nervilia, Plicosepalus, Pachites, Platycoryne

• • subfamily Epidendroideae Phalaenopsis

• Xanthorrhoeaceae
  • subfamily Asphodeloideae: Aloe (succulents and succulent geophytes), Astroloba, × Astroworthia, Bulbine (succulent geophytes, succulents, and geophytes), Bulbinella (geophyte), Chortolirion (succulent geophytes), Gasteria, Haworthia, Trachyandra (succulent geophytes and succulents),
  • subfamily Xanothorrhoeoidae: Xanthorrhoea

Order Asterales

• Asteraceae: Arctotheca, Baeriopsis, Cadiscus, Chrysanthemoides, Coulterella, Crassocephalum, Didelta, Emilia, Eremothamnus, Gymnodiscus, Gynura, Hillardiella (geophyte), Lopholaena, Monoculus, Nidorella, Osteospermum, Othonna (succulents and succulent geophytes), Phaneroglossa, Poecilolepis, Polyachyrus, Pteronia, Senecio, Solanecio,Tripteris

• Campanulaceae: Brighamia

Order Brassicales

• Brassicaceae: Heliophila, Lepidium

• Capparidaceae: Maerua

• Caricaceae: Carica, Jacarathia

• Moringaceae: Moringa

Order Caryophyllales

• Aizoaceae: Corbichonia, Gisekia, Herreanthus, Limeum, Ophthalmophyllum, Saphesia
  • subfamily Aizooideae: Acrosanthes, Aizoanthemum, Aizoon, Galenia, Gunniopsis, Plinthus, Tetragonia
  • subfamily Mesembryanthemoideae (syn. Mesembryanthemaceae): Aptenia, Aridaria, Aspazoma, Brownanthus, Calamophyllum, Caulipsilon, Conophytum, Dactylopsis, Erepsia, Hameria, Hartmanthus, Hymenogyne, Marlothistela, Mesembryanthemum, Phiambolia, Phyllobolus, Prenia, Psilocaulon, Ruschiella, Sarozona, Sceletium, Synaptophyllum
  • subfamily Ruschioideae:
    • tribe Apatesieae: Apatesia, Carpanthea, Caryotophora, Conicosia, Hymenogyne, Saphesia, Skiatophytum
    • tribe Dorotheantheae: Aethephyllum Cleretum Dorotheanthus
    • tribe Ruschiae: Acrodon, Aloinopsis, Amphibolia, Antegibbaeum, Antimima, Arenifera, Argyroderma, Astridia, Bergeranthus, Bijlia, Braunsia, Brianhuntleya, Carpobrotus, Carruanthus, Cephalophyllum, Cerochlamys, Chasmatophyllum, Cheiridopsis, Circandra, Conophytum, Corpuscularia, Cylindrophyllum, Delosperma, Dicrocaulon, Didymaotus, Dinteranthus, Diplosoma, Disphyma, Dracophilus, Drosanthemum, Eberlanzia, Ebracteola, Enarganthe, Erepsia, Esterhuysenia, Faucaria, Fenestraria, Frithia, Gibbaeum, Glottiphyllum, Hallianthus, Hereroa, Ihlenfeldtia, Imitaria, Jacobsenia, Jensenobotrya, Jordaaniella, Juttadinteria, Khadia, Lampranthus, Lapidaria (plant), Leipoldtia, Lithops, Machairophyllum, Malephora, Mestoklema, Meyerophytum, Mitrophyllum, Monilaria, Mossia, Muiria, Namaquanthus, Namibia, Nananthus, Nelia, Neohenricia, Octopoma, Odontophorus, Oophytum, Ophthalmophyllum, Orthopterum, Oscularia, Ottosonderia, Pleiospilos, Polymita, Psammophora, Rabiea, Rhinephyllum, Rhombophyllum, Ruschia, Ruschianthemum, Ruschianthus, Schlechteranthus, Schwantesia, Scopelogena, Smicrostigma, Stayneria, Stoeberia, Stomatium Tanquana Titanopsis, Trichodiadema, Vanheerdea, Vanzijlia, Vlokia, Wooleya, Zeuktophyllum
  • subfamily Sesuvioideae: Cypselea, Sesuvium, Trianthema, Tribulocarpus, Zaleya

• Amaranthaceae:
  • subfamily Amaranthoideae: Arthraerva
  • subfamily Chenopodioideae (family Chenopodiaceae):) Atriplex, Chenopodium, Dissocarpus, Einadia, Enchylaena, Eremophea, Halopeplis, Maireana, Malacocera, Neobassia, Osteocarpum, Rhagodia, Roycea, Halosarcia, Salicornia, Salsola, Sarcocornia, Sclerochlamys, Sclerolaena, Suaeda, Tecticornia, Threlkeldia

• Basellaceae: Anredera, Basella

• Cactaceae: Acanthocalycium, Acanthocereus, Ariocarpus, Armatocereus, Arrojadoa, Arthrocereus, Astrophytum, Austrocactus, Aztekium, Bergerocactus, Blossfeldia, Brachycereus, Browningia, Brasilicereus, Calymmanthium, Carnegiea, Cephalocereus, Cephalocleistocactus, Cereus, Cintia, Cipocereus, Cleistocactus, Coleocephalocereus, Copiapoa, Corryocactus, Coryphantha, Dendrocereus, Denmoza, Discocactus, Disocactus, Echinocactus, Echinocereus, Echinopsis, Epiphyllum, Epithelantha, Eriosyce, Escobaria, Escontria, Espostoa, Espostoopsis, Eulychnia, Facheiroa, Ferocactus, Frailea, Geohintonia, Gymnocalycium, Haageocereus, Harrisia, Hatiora, Hylocereus, Jasminocereus, Lasiocereus, Leocereus, Lepismium, Leptocereus, Leuchtenbergia, Lophophora, Maihuenia, Malacocarpus, Mammillaria, Mammilloydia, Matucana, Melocactus, Micranthocereus, Mila, Monvillea, Myrtillocactus, Neobuxbaumia, Neolloydia, Neoraimondia, Neowerdermannia, Obregonia, Opuntia, Oreocereus, Oroya, Ortegocactus, Pachycereus, Parodia, Pediocactus, Pelecyphora, Peniocereus, Pereskia, Pereskiopsis, Pilosocereus, Polaskia, Praecereus, Pseudoacanthocereus, Pseudorhipsalis, Pterocactus, Pygmaeocereus, Quiabentia, Rauhocereus, Rebutia, Rhipsalis, Samaipaticereus, Schlumbergera, Sclerocactus, Selenicereus, Stenocactus, Stenocereus, Stephanocereus, Stetsonia, Strombocactus, Tacinga, Thelocactus,Trichocereus Turbinicarpus, Uebelmannia, Weberbauerocereus, Weberocereus, Yungasocereus

• Didiereaceae: Alluaudia, Alluaudiopsis, Decaria, Didierea

• Molluginaceae: Hypertelis

• Phytolaccaceae: Phytolacca

• Portulacaceae: Amphipetalum, Anacampseros, Avonia, Calyptrotheca, Ceraria, Cistanthe, Calandrinia, Dendroportulaca, Grahamia, Lewisia, Parakeelya, Portulaca, Portulacaria, Schreiteria, Talinella, Talinum

Order Commelinales

• Commelinaceae: Aneilema, Callisia, Cyanotis, Tradescantia, Tripogandra

Order Cornales

• Loasaceae: Schismocarpus

Order Cucurbitales

• Begoniaceae: Begonia

• Cucurbitaceae: Acanthosicyos, Apodanthera, Brandegea, Cephalopentandra, Ceratosanthes, Citrullus, Coccinia, Corallocarpus, Cucumella, Cucumis, Cucurbita, Cyclantheropsis, Dactyliandra, Dendrosicyos, Doyera, Eureindra, Fevillea, Gerrandanthus, Gynostemma, Halosicyos, Ibervilla, Kedostris, Lagenaria, Marah, Momordica, Neoalsomitra, Odosicyos, Parasicyos, Syrigia, Telfairia, Trochomeria, Trochomeriopsis, Tumamoca, Xerosicyos, Zehneria, Zygosicyos

Order Diascoreales

• Dioscoreaceae: Dioscorea

Order Ericales

• Balsaminaceae: Impatiens

• Ericaceae: Sphyrospermum

• Fouquieriaceae: Fouquieria

Order Fabales

• Fabaceae: Delonix, Dolichos, Erythrina, Lotononis, Neorautanenia, Pachyrhizus, Tylosema

Order Gentianales

• Apocynaceae: Adenium, Mandevilla, Pachypodium, Plumeria
  • subfamily Asclepiadoideae (syn. Asclepiadaceae): Absolmsia, Australluma, Aspidoglossum, Aspidonepsis, Baynesia, Brachystelma, Ceropegia, Chlorocyathus, Cibirhiza, Cordylogyne, Cynanchum, Dischidia, Dischidiopsis, Duvaliandra, Eustegia, Fanninia, Fockea, Glossostelma, Hoya, Ischnolepis, Lavrania, Marsdenia, Miraglossum, Odontostelma, Ophionella, Orbeanthus, Pachycarpus, Parapodium, Periglossum, Petopentia, Raphionacme, Riocreuxia, Sarcorrhiza, Schizoglossum, Schlechterella, Stathmostelma, Stenostelma, Stomatostemma, Trachycalymma, Trichocaulon, Tylophora, Woodia, Xysmalobium
    • tribe Asclepiadeae:
      • subtribe Asclepiadne: Asclepias,
      • subtribe Cynanchinae: Sarcostemma,
      • subtribe Gonolobinae: Matelea,
    • tribe Maxillarieae:
      • subtribe Lycastinae: Rudolfiella
    • tribe Stapeliae: Angolluma, Caralluma, Desmidorchis, Duvalia, Echidnopsis, Edithcolea, Frerea, Hoodia, Huernia, Huerniopsis, Larryleachia, Notechidnopsis, Orbea (plant), Orbeopsis, Piaranthus, Pachycymbium, Pectinaria, Pseudolithos, Pseudopectinaria, Quaqua, Rhytidocaulon, Stapelia, Stapelianthus, Stapeliopsis, Tavaresia, Tridentea, Tromotriche, Whitesloanea
  • subfamily Periplocoideae:
    • tribe Cryptolepideae: Cryptolepis

• Rubiaceae: Anthorrhiza, Anthospermum, Hydnophythum, Hydrophylax, Myrmecodia, Myrmephythum, Phylohydrax, Squamellaria

Order Geraniales

• Geraniaceae: Monsonia, Pelargonium (succulents and geophytes), Sarcocaulon

Order Lamiales

• Gesneriaceae: Aeschynanthus, Alsobia, Chirita, Codonanthe, Columnea, Nematanthus, Sinningia, Streptocarpus

• Lamiaceae: Aeollanthus, Dauphinea, Perrierastrum, Plectranthus, Rotheca, Solenostemon, Tetradenia, Thorncroftia

• Lentibulariaceae

• Pedaliaceae: Holubia, Pterodiscus, Sesamothamnus, Uncarina

Order Malpighiales

• Euphorbiaceae: Cnidoscolus, Euphorbia, Jatropha, Monadenium, Pedilanthus, Phyllanthus, Synadenium

• Passifloraceae: Adenia

• Phyllanthaceae: Phyllanthus

Order Malvales

• Cochlospermaceae

• Malvaceae: Adansonia, Cavanillesia, Ceiba, Pseudobombax

• • subgroup Sterculiaceae: Brachychiton, Sterculia

Order Myrtales

• Melastomataceae: Medinilla

Order Oxalidales

• Oxalidaceae (geophytes): Oxalis

Order Piperales

• Piperaceae: Peperomia

Order Poales

• Bromeliaceae: Abromeitiella, Aechmea, Ananas, Catopsis, Connellia, Dyckia, Hechtia, Neoregelia, Puya, Tillandsia, Vriesea

• Poaceae: Dregeochloa

Order Ranunculales

• Menispermaceae: Chasmanthera, Stephania, Tinospora

Order Rosales

• Moraceae: Dorstenia, Ficus

• Urticaceae: Laportea, Obetia, Pilea, Pouzolzia, Sarcopilea

Order Santalales

• Loranthaceae: Actinanthella, Agelanthus, Erianthemum, Helixanthera, Moquiniella, Oncocalyx, Pedistylis, Plicosepalus, Septulina, Tapinanthus, Vanwykia

• Viscaceae(syn. Santalaceae): Viscum

Order Sapindales

• Anacardiaceae: Operculicaria, Pachycormus

• Burseraceae: Boswellia, Bursera, Commiphora

• Meliaceae: Entandrophragma

• Sapindaceae: Erythrophysa

Order Saxifragales

• Crassulaceae: Adromischus, Aeonium, Afrovivella, Aichryson, Bryophyllum, Cotyledon, Crassula, Cremnophila, × Cremnosedum, Dudleya, Echeveria, Graptopetalum, Greenovia, Hylotelephium, Hypagophytum, Jovibarba, Kalanchoe, Lenophyllum, Meterostachys, Monanthes, Orostachys, Pachyphytum, Perrierosedum, Phedimus, Pistorinia, Prometheum, Pseudosedum, Rhodiola, Rosularia, Sedella, Sedum, Sempervivum, Sinocrassula, Thompsonella, Tylecodon, Umbilicus, Villadia

• Saxifragaceae

Order Solanales

• Convolvulaceae: Ipomoea, Merremia, Stictocardia, Turbina

• Solanaceae: Nolana

Order Vitales

• Vitaceae: Cissus, Cyphostemma

Order Zygophyllales

• Zygophyllaceae: Augea, Seetzenia, Zygophyllum

(unplaced order)* Boraginaceae: Heliotropium (unplaced order)* Icacinaceae: Pyrenacantha (geophyte)

For some families and subfamilies, most members are succulent; for example the Cactaceae, Agavoideae, Aizoaceae, and Crassulaceae.

The table below shows the number of succulent species found in some families:

Family or subfamily	Succulent #	Modified parts	Distribution
Agavoideae	300	Leaf	North and Central America
Cactaceae	1600	Stem (root, leaf)	The Americas
Crassulaceae	1300	Leaf (root)	Worldwide
Aizoaceae	2000	Leaf	Southern Africa, Australia
Apocynaceae	500	Stem	Africa, Arabia, India, Australia
Didiereaceae	11	Stem	Madagascar (endemic)
Euphorbiaceae	> 1000	Stem and/or leaf and/or root	Australia, Africa, Madagascar, Asia, the Americas, Europe
Xanthorrhoeaceae	500+	Leaf	Africa, Madagascar, Australia
Portulacaceae	?	Leaf and stem	The Americas, Australia, Africa

See also

• Cactus and Succulent Society of America
• Crassulacean acid metabolism

Bibliography

• Anderson, Miles (1999), Cacti and Succulents : Illustrated Encyclopedia, Oxford: Sebastian Kelly, ISBN 978-1-84081-253-4
• Beentje, Henk (2010), The Kew Plant Glossary, Richmond, Surrey: Royal Botanic Gardens, Kew, ISBN 978-1-84246-422-9
• Compton, R.H., ed. (n.d.), Our South African Flora, Cape Times Ltd, OCLC 222867742 (publication date also given as 1930s or 1940s)
• Hecht, Hans (1994), Cacti & Succulents (p/b ed.), New York: Sterling, ISBN 978-0-8069-0549-5
• Hewitt, Terry (1993), The Complete Book of Cacti & Succulents, London: Covent Garden Books, ISBN 978-1-85605-402-7
• Innes, Clive; Wall, Bill (1995), Cacti, Succulents and Bromeliads, London: Cassell for the Royal Horticultural Society, ISBN 978-0-304-32076-9 {{citation}}: Unknown parameter |lastauthoramp= ignored (|name-list-style= suggested) (help)
• Jacobsen, Hermann (1960), A Handbook of Succulent Plants (Vols 1–3), Poole, Dorset: Blandford Press, ISBN 978-0-7137-0140-1
• Martin, Margaret J.; Chapman, Peter R. (1977), Succulents and their cultivation, London: Faber & Faber, ISBN 978-0-571-10221-1 {{citation}}: Unknown parameter |lastauthoramp= ignored (|name-list-style= suggested) (help)
• Rowley, Gordon D. (1980), Name that Succulent, Cheltenham, Glos.: Stanley Thornes, ISBN 978-0-85950-447-8

External links

• Drought Smart Plants
• Cacti & Succulent Picture Gallery
• Cactus and Succulent Field Number Database
• Definition of a Succulent
• Cactus and Succulent website with plenty of information
• A site about growing and propagating succulents