The genus Sedum L. (Crassulaceae, subfamily Sempervivoideae) is by far the largest genus in the family, with approximately 488 accepted species according to Plants of the World Online (POWO, December 2025). The generic name derives from the Latin sedere, ‘to sit’, in reference to the manner in which many species sit on rocks and walls. The genus was described by Carl von Linné in the first edition of Species Plantarum (1753) with 15 species, divided into two groups based on leaf morphology: Planifolia (flat-leaved) and Teretifolia (cylindrical-leaved).
The taxonomic history of Sedum is among the most complex and contentious in all of botany. Three decades of molecular phylogenetic work have established beyond doubt that Sedum as traditionally circumscribed is massively polyphyletic — what Messerschmid et al. (2020) memorably termed ‘Linnaeus’s folly’. Of the 15 species originally described by Linnaeus, ten fall into four different major clades within the Sempervivoideae, while the remaining five are now classified in segregate genera (Hylotelephium, Phedimus). Species of Sedum are scattered across all five major lineages of the subfamily: the Telephium clade, the Petrosedum clade, the Sempervivum clade (marginal), the Aeonium clade, and the Leucosedum plus Acre clades.
The most comprehensive phylogenetic study to date is that of Messerschmid et al. (2020, Taxon 69: 1010–1066), which sampled 80% of all infrageneric taxa described in Sedum using ITS and three plastid markers. The study confirmed that Sedum species never form a monophyletic group in any of the five clades but are either scattered across phylogenetic trees or form basal grades. Notable segregate genera recognised from former Sedum species include Hylotelephium H.Ohba (~33 species), Phedimus Raf. (~19 species), Petrosedum Grulich (~17 species), Rhodiola L. (~60 species), Dudleya Britton & Rose (~47 species) and Villadia Rose (~40 species). POWO currently retains a broad circumscription of Sedum pending resolution of the ‘Sedum problem’.
The main historical infrageneric classifications are those of Berger (1930, 22 ‘Reihe’ or series), Fröderström (1935, 9 sections in a broad genus) and Ohba (1978). None of these are phylogenetically sound. Two radical solutions have been proposed: (1) splitting Sedum into numerous smaller genera matching monophyletic lineages, or (2) expanding Sedum sensu latissimo to encompass all taxa within tribe Sedeae (~755 species), absorbing genera such as Echeveria, Pachyphytum, Graptopetalum and Dudleya. Neither solution has been formally adopted, and the taxonomy remains in flux.
Distribution
Sedum is distributed primarily in the Northern Hemisphere, with major centres of diversity in Mexico and Central America (~150 species, mostly in the Acre clade), East Asia (China, Japan, Korea, ~120 species), and the Mediterranean–European region (~55 species). Smaller numbers extend to the Himalayas, Central Asia, North Africa and the Arabian Peninsula. A few species occur in the Southern Hemisphere in Africa (notably Sedum caeruleum L. in North Africa and Mediterranean islands, and Sedum modestum Ball in Morocco) and South America (Sedum spp. in the Andes).
The genus occupies an extraordinarily broad range of habitats, from sea-level rock pools and coastal cliffs to alpine screes above 16,000 ft (5,000 m) in the Himalayas. Stonecrops are quintessential saxicolous plants, colonising thin soils on rock outcrops, walls, rooftops, gravel and crevices where competition from deeper-rooted vegetation is minimal. Some species are truly aquatic or semi-aquatic (Sedum villosum L.), while others inhabit deep forest shade (Sedum cepaea L.).
Several species are widely naturalised beyond their native range, particularly Sedum acre L. (Europe to Central Asia, widely naturalised in North America), Sedum sarmentosum Bunge (East Asia, naturalised in eastern North America) and Sedum album L. (Europe, naturalised worldwide). The extensive use of Sedum species in green roofs and horticultural ground cover has further expanded their global distribution.
Ecology and Biology
Sedum species are annual, biennial or perennial herbs, rarely subshrubs. They are characterised by succulent leaves and stems, with leaves typically alternate and spirally arranged (unlike the opposite leaves of Crassula). Flowers are usually pentamerous (rarely tetramerous or hexamerous), with free petals, typically twice as many stamens as petals (obdiplostemony), and free carpels. Flower colour spans white, yellow, pink, red and purple, with yellow being the most common.
Pollination is primarily by insects (bees, flies, butterflies, beetles), and flowers typically produce nectar in nectariferous scales at the base of the carpels. Many species are highly efficient colonisers of disturbed or skeletal substrates, spreading by fragmentation (stem or leaf cuttings root readily on contact with soil), stolons, offsets or prolific seed production. Some European species (Sedum acre, Sedum album) form extensive mats on rock surfaces and walls, playing an important role in primary ecological succession.
Life-history strategies within the genus are exceptionally diverse: most species are perennial and evergreen, but annual (Sedum cespitosum (Cav.) DC., Sedum atratum L.) and biennial (Sedum rubens L.) species exist. Chromosome numbers are highly variable and polyploidy is rampant, which has contributed to the taxonomic difficulties of the genus.
Adaptations to Aridity and CAM Photosynthesis
As leaf-succulents, Sedum species possess a range of xerophytic adaptations: succulent leaves with high water-storage capacity, thick cuticle (often pruinose or waxy), low stomatal density, and a compact growth form reducing the transpiring surface. Many species possess CAM (Crassulacean Acid Metabolism) or facultative CAM, with some shifting between C3 and CAM depending on water availability. Species from arid Mediterranean and Mexican habitats tend toward obligate or strong facultative CAM, while species from mesic alpine or forest habitats are predominantly C3.
The succulence and drought tolerance of Sedum have made them the premier genus for green roof technology worldwide. Species such as Sedum album, Sedum acre, Sedum sexangulare L., Sedum spurium M.Bieb. (now Phedimus spurius) and Sedum kamtschaticum Fisch. (now Phedimus kamtschaticus) are among the most commonly planted green-roof species, valued for their ability to survive on minimal substrate depth, tolerate extreme heat and cold, and reduce stormwater runoff.
Phylogenetic Placement and the ‘Sedum Problem’
Species currently placed in Sedum (sensu POWO) are found in four of the five major crown clades of subfamily Sempervivoideae, plus the Aeonium clade. The following summary follows Messerschmid et al. (2020) and Mort et al. (2001).
Acre Clade (Tribe Sedeae pro parte)
The Acre clade is the core of Sedum in the strict sense, containing the type species Sedum acre L. This is the largest and most taxonomically complex clade, encompassing the majority of Northern Hemisphere Sedum species plus the enormous New World radiation of genera such as Echeveria DC. (~170 species), Dudleya Britton & Rose (~47 species), Graptopetalum Rose (~19 species), Pachyphytum Link, Klotzsch & Otto (~20 species) and Villadia Rose (~40 species). Sedum species in this clade are neither monophyletic nor form a cohesive group — they are interspersed with and often grade into other genera. The Mexican Sedum species (~150 species) form several independent lineages within the Acre clade, some closely related to Echeveria, others to Villadia or Pachyphytum.
Representative European/Mediterranean species: Sedum acre L., Sedum album L., Sedum alpestre Vill., Sedum anglicum Huds., Sedum annuum L., Sedum atratum L., Sedum brevifolium DC., Sedum caespitosum (Cav.) DC., Sedum dasyphyllum L., Sedum gypsicola Boiss. & Reut., Sedum hirsutum All., Sedum hispanicum L., Sedum litoreum Guss., Sedum magellense Ten., Sedum monregalense Balb., Sedum rubens L., Sedum sexangulare L., Sedum villosum L.
Representative Asian species: Sedum alfredii Hance, Sedum arisanense Yamam., Sedum formosanum N.E.Br., Sedum japonicum Sieb. ex Miq., Sedum lineare Thunb., Sedum makinoi Maxim., Sedum multicaule Wall. ex Lindl., Sedum oryzifolium Makino, Sedum polytrichoides Hemsl., Sedum sarmentosum Bunge, Sedum subtile Miq.
Representative Mexican/New World species: Sedum adolphi Raym.-Hamet, Sedum allantoides Rose, Sedum bourgaei Hemsl., Sedum burrito Moran, Sedum clavatum R.T.Clausen, Sedum commixtum Moran & Hutchison, Sedum confusum Hemsl., Sedum furfuraceum Moran, Sedum griseum Praeger, Sedum hernandezii Meyrán, Sedum hintonii R.T.Clausen, Sedum morganianum E.Walther, Sedum nussbaumerianum Bitter, Sedum oxypetalum Kunth, Sedum pachyphyllum Rose, Sedum palmeri S.Watson, Sedum praealtum A.DC., Sedum rubrotinctum R.T.Clausen, Sedum stahlii Solms, Sedum treleasei Rose.
Leucosedum Clade (Tribe Sedeae pro parte)
The Leucosedum clade is sister to the Acre clade and contains a smaller number of Sedum species, mainly European and Mediterranean, characterised by white or pinkish flowers and a generally more mesic ecology than the Acre clade species. Segregate genera include Prometheum (H.Ohba) H.Ohba (~6 species) and Rosularia (DC.) Stapf (~40 species). The boundaries between Sedum sensu stricto and the Leucosedum clade genera remain poorly defined.
Representative species: Sedum amplexicaule DC., Sedum andegavense (DC.) Desv., Sedum arenarium Brot., Sedum bracteatum Viv., Sedum caeruleum L., Sedum cepaea L., Sedum fragrans ‘t Hart, Sedum glanduliferum Guss., Sedum laconicum Boiss. & Heldr., Sedum pubescens Vahl, Sedum stellatum L., Sedum tenuifolium (Sm.) Strobl.
Petrosedum Clade
The Petrosedum clade contains species formerly placed in Sedum section Sedum or series Rupestria Berger, now often segregated as the genus Petrosedum Grulich (~17 species). These are robust European perennials with typically yellow flowers and large, terete or somewhat flattened, deciduous leaves. The clade is well supported as monophyletic and its treatment at generic rank is widely accepted, although POWO has recently re-accepted some species under Petrosedum.
Species (as Sedum or Petrosedum): Sedum forsterianum Sm. (Petrosedum forsterianum), Sedum montanum Songeon & E.P.Perrier (Petrosedum montanum), Sedum ochroleucum Chaix (Petrosedum ochroleucum), Sedum rupestre L. (Petrosedum rupestre), Sedum sediforme (Jacq.) Pau (Petrosedum sediforme), Sedum thartii ‘t Hart (Petrosedum thartii).
Telephium Clade (Tribe Umbiliceae)
The Telephium clade is phylogenetically distant from the core Sedum in the Acre clade and is placed in a separate tribe (Umbiliceae). Species once classified as Sedum in this clade have mostly been transferred to segregate genera: Hylotelephium H.Ohba (~33 species, including the former Sedum telephium L., Sedum spectabile Boreau and Sedum sieboldii Sweet ex Hook.), Phedimus Raf. (~19 species, including the former Sedum spurium M.Bieb. and Sedum kamtschaticum Fisch.), and Rhodiola L. (~60 species, including the widely used Rhodiola rosea L., formerly Sedum roseum). These genera are not closely related to Sedum sensu stricto and their continued use is strongly supported by molecular data.
Segregated species (former Sedum): Hylotelephium telephium (L.) H.Ohba (= Sedum telephium), Hylotelephium spectabile (Boreau) H.Ohba (= Sedum spectabile), Hylotelephium sieboldii (Sweet ex Hook.) H.Ohba (= Sedum sieboldii), Hylotelephium erythrostictum (Miq.) H.Ohba (= Sedum erythrostictum), Phedimus spurius (M.Bieb.) ‘t Hart (= Sedum spurium), Phedimus kamtschaticus (Fisch.) ‘t Hart (= Sedum kamtschaticum), Phedimus aizoon (L.) ‘t Hart (= Sedum aizoon), Rhodiola rosea L. (= Sedum roseum).
Aeonium Clade
A small number of Sedum species from North Africa and Macaronesia fall within the Aeonium clade, rather than with the core Sedum. These include Sedum modestum Ball, Sedum jaccardianum Maire & Wilczek and Sedum surculosum Coss., all from the western Mediterranean region. These species are phylogenetically closer to the Macaronesian genera Aeonium, Aichryson and Monanthes than to other Sedum. Their eventual transfer to a separate genus or absorption into the Aeonium clade is anticipated.
Horticultural and Economic Importance
Sedum species are among the most widely cultivated succulent plants worldwide, valued for their drought tolerance, ease of propagation, diversity of forms and colourful foliage. Key horticultural uses include: green roofs (where Sedum species dominate globally due to their shallow-rooting, drought-tolerant mats), rock gardens, alpine gardens, container planting, ground cover, and indoor houseplants. Major ornamental species include Sedum morganianum E.Walther (‘burro’s tail’), Sedum rubrotinctum R.T.Clausen (‘jelly beans’), Sedum adolphi Raym.-Hamet (‘golden sedum’), Sedum sieboldii Sweet ex Hook. (now Hylotelephium sieboldii), and Sedum spectabile Boreau (now Hylotelephium spectabile, the ‘ice plant’ of autumn borders).
Several Sedum species have traditional medicinal or culinary uses: Sedum acre has been used in European folk medicine (though it contains piperidine alkaloids and is mildly toxic), and Sedum sarmentosum is used in traditional Chinese medicine for liver disorders. Sedum alfredii Hance is a hyperaccumulator of zinc and cadmium, studied for phytoremediation of heavy-metal-contaminated soils.
Major Botanical Collections
Royal Botanic Gardens, Kew (K), United Kingdom. Major herbarium and living collections, with type specimens of many European and Asian species. POWO database serving as the global reference.
Muséum National d’Histoire Naturelle, Paris (P), France. Historic herbarium containing type specimens of de Candolle, Praeger and Raym.-Hamet.
Missouri Botanical Garden (MO), St. Louis, USA. Extensive herbarium holdings for New World Sedum and related genera (Echeveria, Dudleya, Villadia), particularly from Mexico.
Institute of Botany, Chinese Academy of Sciences (PE), Beijing, China. Reference collection for East Asian Sedum, supporting the Flora of China treatment.
Sukkulenten-Sammlung Zürich, Switzerland. Major living collection of Crassulaceae, with comprehensive Sedum representation.
Botanischer Garten Berlin-Dahlem, Germany. Historic collections of European and Central Asian Sedum, with herbarium (B) containing Berger’s types.
Jardín Botánico de la UNAM, Mexico City, Mexico. Reference collection for Mexican Sedum and related genera.
Authority Sites and Online Resources
Plants of the World Online (POWO) — Royal Botanic Gardens, Kew
https://powo.science.kew.org/taxon/…
International Crassulaceae Network (ICN) — Sedum
https://www.crassulaceae.ch/de/…
Flora of China — Crassulaceae
http://www.efloras.org/…
Flora of North America — Crassulaceae
http://www.efloras.org/…
iNaturalist — Sedum observations
https://www.inaturalist.org/taxa/48618-Sedum
World of Succulents — Sedum
https://worldofsucculents.com/genera/sedum/
LLIFLE — Encyclopedia of Living Forms
https://www.llifle.com/Encyclopedia/SUCCULENTS/…
GBIF — Global Biodiversity Information Facility
https://www.gbif.org/
Tropicos — Missouri Botanical Garden
https://www.tropicos.org/
Biodiversity Heritage Library (BHL)
https://www.biodiversitylibrary.org/
Bibliography
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