In botany, succulent plants, also known as succulents, are with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions. The word succulent comes from the Latin word sucus, meaning "juice" or "sap".
Succulents may store water in various structures, such as leaf and Plant stem. The water content of some succulent organs can get up to 90–95%,[Jacobsen Handbook op.cit. Volume 3 P. 1259] Some definitions also include , thus that survive unfavorable periods by dying back to underground (caudex) may be regarded as succulents. The habitats of these water-preserving plants are often in areas with high temperatures and low rainfall, such as , but succulents may be found even in Alpine climate ecosystems growing in rocky or sandy soil. Succulents are characterized by their ability to thrive on limited water sources, such as mist and dew, which makes them equipped to survive in that contain scarce water sources.
Succulents are not a taxonomic category, since the term describes only the attributes of a particular species; some species in a genus such as Euphorbia, or family such as Asphodelaceae may be succulent, whereas others are less so or not at all. Multiple plant families contain both succulent and non-succulent species.
Definition
By definition, succulent plants are
drought-resistant plants in which the leaves, stem, or roots have become more than usually fleshy by the development of water-storing tissue. Other sources exclude roots as in the definition "a plant with thick, fleshy and swollen stems and/or leaves, adapted to dry environments". The difference affects the relationship between succulents and "
Storage organ"–plants that survive unfavorable seasons as a resting bud on an underground organ.
The underground organs, such as , , and , are often fleshy with water-storing tissues. Thus, if roots are included in the definition, many Storage organ would be classed as succulents. Plants adapted to living in dry environments such as succulents, are termed . 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.
Some who grow succulents as a hobby may use the term in a different way from botanists. In Horticulture use, the term succulent regularly excludes cacti. For example, Jacobsen's three volume Handbook of Succulent Plants does not include cacti. Many books covering the cultivation of these plants include "cacti (cactus) and succulents" as the title or part of the title. In botanical terminology, cacti are succulents, but not the reverse, as many succulent plants are not cacti. Cacti form a Monophyly group and apart from one species are native only to the New World, the Americas, but through parallel evolution similar looking plants in completely different families like the Apocynaceae evolved in the Old World.
A further difficulty for general identification is that plant families are neither succulent nor non-succulent and can contain both. In many genera and families, there is a continuous gradation from plants with thin leaves and normal stems to those with very clearly thickened and fleshy leaves or stems. The succulent characteristic becomes meaningless for dividing plants into genera and families. Different sources may classify the same species differently. Species with intermediate characteristics such as somewhat fleshy leaves or stems may be described as semi-succulent.
Horticulturists often follow commercial conventions and may exclude other groups of plants such as bromeliads, that scientifically are considered succulents. A practical horticultural definition has become "a succulent plant is any desert plant that a succulent plant collector wishes to grow", without any consideration of scientific classifications. Commercial presentations of "succulent" plants will present those that customers commonly identify as such. Plants offered commercially then as "succulents", such as hen and chicks, will less often include geophytes, in which the swollen storage organ is wholly underground, but will include plants with a caudex, that is a swollen above-ground organ at soil level, formed from a stem, a root, or both.
Appearance
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:
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crassulacean acid metabolism (CAM) to minimize water loss
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absent, reduced, or cylindrical-to-spherical leaves
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reduction in the number of
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stems as the main site of photosynthesis, rather than leaves
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compact, reduced, cushion-like, columnar, or spherical growth form
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ribs enabling rapid increases in plant volume and decreasing surface area exposed to the sun
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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 may create shade
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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
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ability to remain plump and full of water even with high internal temperatures (e.g., )
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very impervious outer Plant cuticle (skin)
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fast wound sealing and healing
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Mucilage, which retain water abundantly
Habitat
Other than in
Antarctica, succulents can be found within each continent. According to the World Wildlife Fund,
South Africa is home to around a third of all succulent species, most residing in the
succulent Karoo biome.
While it is often thought that most succulents come from dry areas such as
,
semi-desert, and
desert, the world's driest areas do not make for proper succulent habitats, mainly due to the difficulty such low growing plants or seedlings would have to thrive in environments where they could easily be covered by sand.
Australia, the world's driest inhabited continent, hosts very few native succulents due to the frequent and prolonged droughts. Even Africa, the continent with the most native succulents, does not host many of the plants in its most dry regions.
Occasionally, succulents may occur as , growing on other plants with limited or no contact with the ground, and being dependent on their ability to store water and gaining nutrients by other means; it is seen in Tillandsia and Rhipsalis. Succulents also occur as inhabitants of sea and , which are exposed to high levels of dissolved minerals that are deadly to many other plant species. California is home to close to hundred succulent species that are native to the state, many of them live in coastal environments.
Conservation
There is a thriving illegal trade in cacti and succulents.
In South Africa, several species of succulent have been threatened with extinction due to
poaching from the wild for the
black market and mining related activities. The plants are mainly sold to collectors in Asian countries, where there has been a high demand for them.
Since 1974, it is illegal to be in possession of protected succulents such as the
Conophytum without authorisation in the
Western Cape and
Northern Cape, the two South African provinces where they grow.
Families and genera
There are approximately sixty different plant families that contain succulents.
Plant orders, families, and genera in which succulent species occur are listed below.
Order Alismatales
Order Apiales
Order Arecales (also called Principes)
Order Asparagales
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Amaryllidaceae (geophytes): Amaryllis, Boophone, Clivia, Crinum, Cryptostephanus, Cyrtanthus, Haemanthus, Rauhia, Scadoxus, Stenomesson
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Asparagaceae
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Agavoideae: Agave, Beschorneria, Furcraea, Hesperaloe, Hesperoyucca, Manfreda, Polianthes, Yucca
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Lomandroideae: Cordyline
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Nolinoideae: Beaucarnea, Calibanus, Dasylirion, Dracaena, Nolina
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Scilloideae: Albuca, Bowiea, Daubenya, Drimia, Eucomis, Lachenalia, Ledebouria, Massonia, Muscari, Ornithogalum, Scilla, Drimia, Veltheimia
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Doryanthaceae: Doryanthes
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Orchidaceae: Acampe, Aerangis, Ansellia, Bolusiella, Bulbophyllum, Cirrhopetalum, Calanthe, Cyrtorchis, Dendrobium cucumerinum, Eulophia, Liparis, Oberonia, Oeceoclades, Polystachya, Tridactyle, Vanilla
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Asphodelaceae
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subfamily Asphodeloideae: Aloe (succulents and succulent geophytes), Astroloba, Tulista, × Astrolista, Bulbine (succulent geophytes, succulents, and geophytes), Bulbinella (geophyte), Chortolirion (succulent geophytes), Gasteria, Gonialoe, Haworthia, Trachyandra (succulent geophytes and succulents),
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subfamily Xanothorrhoeoidae: Xanthorrhoea
Order Asterales
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Asteraceae: Arctotheca, Baeriopsis, Chrysanthemoides, Coulterella, Crassocephalum, Curio, Delairea, Didelta, Emilia, Eremothamnus, Gymnodiscus, Gynura, Hillardiella (geophyte), Lopholaena, Monoculus, Nidorella, Osteospermum, Othonna (succulents and succulent geophytes), Phaneroglossa, Poecilolepis, Polyachyrus, Pteronia, Senecio, Solanecio, Tripteris
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Campanulaceae: Brighamia
Order Brassicales
Order Caryophyllales
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Aizoaceae: Corbichonia, Gisekia, Herreanthus, Limeum, Ophthalmophyllum, Saphesia
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subfamily Aizooideae: Acrosanthes, Aizoanthemum, Aizoon, Galenia, Gunniopsis, Plinthus, Tetragonia
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subfamily Mesembryanthemoideae (syn. Mesembryanthemaceae
[ Plants of Southern Africa Retrieved on 2010-1-1]): Aptenia (synonym of Mesembryanthemum), Aridaria, Aspazoma, Brownanthus (synonym of Mesembryanthemum), Calamophyllum, Caulipsilon, Conophytum, Dactylopsis, Erepsia, Hameria, Hartmanthus, Hymenogyne, Marlothistela, Mesembryanthemum, Phiambolia, Phyllobolus, Prenia, Psilocaulon, Ruschiella, Sarozona, Synaptophyllum
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subfamily Ruschioideae:
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tribe Apatesieae: Apatesia, Carpanthea, Caryotophora, Conicosia, Hymenogyne, Saphesia, Skiatophytum
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tribe Dorotheantheae: Aethephyllum Cleretum Dorotheanthus
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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
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subfamily Sesuvioideae: Cypselea, Sesuvium, Trianthema, Tribulocarpus, Zaleya
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Amaranthaceae:
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subfamily Amaranthoideae: Arthraerva
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subfamily Chenopodioideae (family Chenopodiaceae):
[ FloraBase – The Western Australian Flora Retrieved on 2010-1-1]) Atriplex, Chenopodium, Dissocarpus, Einadia, Enchylaena, Eremophea, Halopeplis, Maireana, Malacocera, Neobassia, Osteocarpum, Rhagodia, Roycea, Halosarcia, Salicornia, Salsola, Sarcocornia, Sclerochlamys, Sclerolaena, Suaeda, Tecticornia, Threlkeldia
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Basellaceae: Anredera, Basella
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Cactus: 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, Mammillaria, Matucana, Melocactus, Micranthocereus, Mila, Monvillea, Myrtillocactus, Neobuxbaumia, Neoraimondia, Neowerdermannia, Obregonia, Opuntia, Cylindropuntia, Oreocereus, Oroya, Ortegocactus, Pachycereus, Parodia, Pediocactus, Pelecyphora, Peniocereus, Pereskia, Pereskiopsis, Pilosocereus, Polaskia, Praecereus, Pseudoacanthocereus, Pseudorhipsalis, Pterocactus, Pygmaeocereus, Quiabentia, Rauhocereus, Rebutia, Rhipsalis, Schlumbergera, Sclerocactus, Selenicereus, Stenocactus, Stenocereus, Stephanocereus, Stetsonia, Strombocactus, Tacinga, Thelocactus, Trichocereus Turbinicarpus, Uebelmannia, Weberbauerocereus, Weberocereus
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Didiereaceae: Alluaudia, Alluaudiopsis, Decaria, Didierea
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Molluginaceae: Hypertelis
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Phytolaccaceae: Phytolacca
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Portulacaceae: Amphipetalum, Anacampseros, Avonia, Calyptrotheca, Ceraria, Cistanthe, Calandrinia, Dendroportulaca, Grahamia, Lewisia, Parakeelya,
[ Parakeelya. The Plant List.] Portulaca, Portulacaria, Schreiteria, Talinella, Talinum
Order Commelinales
Order Cornales
Order Cucurbitales
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Begoniaceae: Begonia
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Cucurbitaceae: Acanthosicyos, Apodanthera, Brandegea, Cephalopentandra, Ceratosanthes, Citrullus, Coccinia, Corallocarpus, Cucumis, Cucumis, Cucurbita, Cyclantheropsis, Dactyliandra, Dendrosicyos, Doyera, Eureindra, Fevillea, Gerrandanthus, Gynostemma, Halosicyos, Ibervillea, Kedostris, Lagenaria, Marah, Momordica, Neoalsomitra, Odosicyos, Parasicyos, Syrigia, Telfairia, Trochomeria, Trochomeriopsis, Tumamoca, Xerosicyos, Zehneria, Zygosicyos
Order Dioscoreales
Order Ericales
Order Fabales
Order Filicales
Order Gentianales
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Apocynaceae: Adenium, Mandevilla, Pachypodium, Plumeria
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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 (now in Vincetoxicum), Woodia, Xysmalobium
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tribe Asclepiadeae:
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tribe Maxillarieae:
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tribe Stapelieae: 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
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subfamily Periplocoideae:
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Rubiaceae: Anthorrhiza, Anthospermum, Hydnophytum, Hydrophylax, Myrmecodia, Myrmephytum, Phylohydrax, Squamellaria
Order Geraniales
Order Lamiales
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Gesneriaceae: Aeschynanthus, Alsobia, Chirita, Codonanthe, Columnea, Nematanthus, Sinningia, Streptocarpus
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Lamiaceae: Aeollanthus, Dauphinea, Perrierastrum, Plectranthus, Rotheca, Solenostemon, Tetradenia, Thorncroftia
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Lentibulariaceae
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Pedaliaceae: Holubia, Pterodiscus, Sesamothamnus, Uncarina
Order Malpighiales
Order Malvales
Order Myrtales
Order Oxalidales
Order Piperales
Order Poales
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Bromeliaceae: Abromeitiella, Aechmea, Ananas, Catopsis, Connellia, Dyckia, Hechtia, Neoregelia, Puya, Tillandsia, Vriesea
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Poaceae: Dregeochloa,
[ Dregeochloa pumila. South African National Biodiversity Institute] Laobambos
Order Ranunculales
Order Rosales
Order Santalales
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Loranthaceae: Actinanthella, Agelanthus, Erianthemum, Helixanthera, Moquiniella, Oncocalyx, Pedistylis, Plicosepalus, Septulina, Tapinanthus, Vanwykia
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Viscaceae (syn. Santalaceae): Viscum
Order Sapindales
Order Saxifragales
Afrovivella,
Aichryson,
Cotyledon,
Crassula,
Cremnophila,
Dudleya,
Echeveria,
Graptopetalum,
Greenovia,
Hylotelephium,
Kalanchoe,
Kungia,
Lenophyllum,
Meterostachys,
Monanthes,
Mucizonia,
Orostachys,
Pachyphytum,
Perrierosedum,
Petrosedum,
Phedimus,
Pistorinia,
Prometheum,
Pseudosedum,
Rhodiola,
Rosularia,
Sedella,
Sedum,
Sempervivum,
Sinocrassula,
Thompsonella,
Tylecodon,
Umbilicus,
Villadia,afrovivella
Order Solanales
Order Vitales
Order Zygophyllales
(unplaced order)* Boraginaceae: Heliotropium
(unplaced order)* Icacinaceae: Pyrenacantha (geophyte)
There also were some succulent (but extinct since the end of the Cretaceous):
Order Pinales
Frenelopsis,
Pseudofrenelopsis,
Suturovagina,
Glenrosa
For some families and subfamilies, most members are succulent; for example the Cactus, Agavoideae, Aizoaceae, and Crassulaceae.
The table below shows the number of succulent species found in some families and their native habitat:
|
| North and Central America |
| The Americas |
| Worldwide |
| Southern Africa, Oceania, Chile |
| Africa, Arabia, India, Australia |
| Africa, Madagascar, Australia |
| Madagascar (endemic) |
| Australia, Africa, Madagascar, Asia, the Americas, Europe |
| The Americas, Australia, Africa |
| Worldwide, except Antarctica |
|
Cultivation
Succulents are favored as
for their attractiveness and ease of care. They have been cultivated as houseplants since at least the 17th century.
If properly potted, succulents require little maintenance to survive indoors.
Succulents are very adaptable houseplants and will thrive in a range of indoor conditions.
For most plant owners, over-watering and associated infections are the main cause of death in succulents.
Succulents can be propagated in a number of ways, with vegetative propagation being the most common. This includes cuttings, where a few centimetres of the leafy stem is cut off and left to heal, forming a callus. Following a period of approximately seven days, roots may begin to develop. A second method is division consisting of uprooting an overgrown clump and pulling the stems and roots apart.
A third method is propagation by leaf by allowing the formation of a callus. During this method, a bottom leaf is fully removed from the plant often by twisting or cutting. The leaf then dries out and a callus forms preventing the leaf from absorbing too much moisture and rotting. This method typically takes up to a few weeks to produce healthy roots that would eventually create new plants.
See also
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Cactus and Succulent Society of America
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Crassulacean acid metabolism
Bibliography
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(publication date also given as 1930s or 1940s)
External links
