Genus Crassula

The genus Crassula L. (Crassulaceae, subfamily Crassuloideae) is the second-largest genus in the family Crassulaceae, after Sedum L. It comprises approximately 216 accepted species according to Plants of the World Online (POWO, December 2024), although some recent estimates place the number above 200 depending on circumscription. The generic name derives from the Latin crassus, meaning ‘thick’, in reference to the succulent leaves. The genus was formally described by Carl von Linné in 1753 in the first volume of the Species Plantarum, with ten initial species.

The most comprehensive monographic revision of the genus for southern Africa remains that of Helmut R. Tölken (1977, Contributions from the Bolus Herbarium no. 8; and 1985, Flora of Southern Africa vol. 14), which recognises two subgenera — Crassula and Disporocarpa — subdivided into 20 sections totalling 149 species for southern Africa alone. About twenty additional species are distributed across the world’s temperate regions.

The first broad-sampling phylogenetic study of the genus was that of Bruyns, Hanáček & Klak (2019, Molecular Phylogenetics and Evolution 131: 35–47), covering 68% of known species. This molecular analysis (three chloroplast and two nuclear gene regions) revealed that only 5 of Tölken’s 20 sections are monophyletic, but broadly confirmed the two subgenera. Three major clades (A, B, C) were identified. Clade C, the largest, concentrates the most recent diversification, which mainly occurred within the last 10 million years in the Greater Cape Floristic Region (GCFR).

The genus Tillaea L., formerly considered distinct, was merged into Crassula based on molecular data (Mort et al., 2009). Recent phylogenomic analyses (Ding et al., 2022; Kim et al., 2024) confirm the monophyly of Crassula in the broad sense, including Tillaea, and support the division into two subgenera. However, the sectional classification requires thorough reassessment, as the majority of sections prove to be paraphyletic.

Distribution

The genus Crassula has a disjunct distribution spanning the temperate and subtropical regions of all continents, but with an overwhelming centre of diversity in southern Africa, specifically in the Greater Cape Floristic Region (GCFR) and the Succulent Karoo biome. South Africa alone harbours approximately 150 species — over 70% of the genus’s species-level diversity. Maximum density reaches 66 species per degree square (~37 × 37 mi / 60 × 60 km) in the south-west of the country (Jürgens, 1985), a record of local diversity that places Crassula second only to the Aizoaceae (~1,650 species) among leaf-succulents in southern Africa.

Within southern Africa, species are concentrated in the Fynbos, Succulent Karoo and Nama Karoo biomes, as well as in the coastal regions of the Western Cape, Eastern Cape, Northern Cape, southern Namibia (Richtersveld, Namaqualand, Huns Mountains) and Bushmanland. Elevation ranges from sea level to alpine grasslands above 6,500 ft (2,000 m) in the Drakensberg. Outside southern Africa, a few robust perennial species extend to East Africa (Crassula volkensii, Crassula granvikii), Madagascar (Crassula ankaratrensis, Crassula humbertii), the Arabian Peninsula and northern India (Crassula schimperi).

The cosmopolitan species of the genus are mainly annuals or small perennials of section Tillaea (subgenus Disporocarpa), often aquatic, semi-aquatic or ruderal. Crassula helmsii (Kirk) Cockayne, native to Australasia, has become a highly invasive species in Europe, particularly in the United Kingdom, the Netherlands and Belgium, where it colonises freshwater bodies. Crassula tillaea Lest.-Garl. is the only species native to mainland Europe (circum-Mediterranean region, including southern France). Subgenus Disporocarpa species are found in North America (Crassula connata, Crassula drummondii), South America (Crassula closiana, Crassula venezuelensis), Australia (Crassula sieberiana, Crassula colorata), New Zealand (Crassula moschata, Crassula hunua) and East Asia (Crassula aquatica).

Ecology and Biology

Crassula species occupy a remarkable range of habitats, from coastal deserts to alpine grasslands, from vertical cliff faces to seasonally flooded areas. The common factor is well-drained, often skeletal substrates (quartzite, sandstone or granite outcrops), where competition with mesic grasses and shrubs is reduced.

In southern Africa, the majority of species are associated with the Fynbos biome (winter-rainfall regime) and the Succulent Karoo (winter to bimodal rainfall). Species of section Montana and some of section Crassula (Crassula sarcocaulis, Crassula multicava) extend into the summer-rainfall regions of KwaZulu-Natal and the Drakensberg.

In terms of life-history strategy, the genus presents an unusual mix of annuals (over 25 species) and perennials. Succulent annuals are rare among plants in general, and Crassula possesses the largest number within the Crassulaceae. The analysis of Bruyns et al. (2019) showed that annual species do not form a monophyletic group but appear as early-diverging branches in each of the three major clades, suggesting that the annual strategy is ancestral in the genus and that perenniality evolved independently on multiple occasions.

Pollination in Crassula involves a diverse spectrum of vectors. Species with narrow tubular red corollas (Crassula coccinea, Crassula perfoliata var. minor) are pollinated by diurnal butterflies. Species with white or cream sweetly-scented corollas (Crassula ovata, Crassula arborescens) are mainly visited by bees and flies. Some species with nocturnal flowering and strong scent (section Fasciculares) are probably pollinated by moths. Hydathodes, water-secreting structures characteristic of the genus, play a role in foliar water and dew absorption (Fradera-Soler et al., 2024).

Adaptations to Aridity and CAM Photosynthesis

The genus Crassula is inextricably linked to the discovery of Crassulacean Acid Metabolism (CAM), since it was in members of the family Crassulaceae that this photosynthetic pathway was first described (observations by De Saussure, 1804; Heyne, 1812; the term ‘CAM’ coined by Ranson & Thomas, 1940).

CAM is a CO2-concentrating mechanism that temporally separates primary carbon fixation (nocturnal) from its reduction to sugars (diurnal). At night, stomata open and atmospheric CO2 is fixed by phosphoenolpyruvate carboxylase (PEPC) to form oxaloacetate, which is rapidly reduced to malate and stored in the large vacuoles of mesophyll cells as malic acid. During the day, stomata close (reducing transpirational water loss), malate is exported from the vacuole and decarboxylated, releasing CO2 at high concentration around Rubisco, favouring carboxylation and suppressing photorespiration.

This mechanism gives CAM plants a water-use efficiency (WUE) up to six-fold greater than C3 plants and three-fold greater than C4 plants. The expression of CAM in Crassula varies according to species and environmental conditions. A distinction is drawn between obligate (constitutive) CAM, facultative (drought-inducible) CAM, CAM cycling (diurnal malic acid fluctuations without nocturnal stomatal opening) and CAM idling (stomata closed day and night, recycling internally respired CO2). Some aquatic species, such as Crassula aquatica and Crassula helmsii, perform aquatic CAM, where the limiting factor is dissolved CO2 rather than water availability.

In addition to CAM, Crassula species display a suite of co-adaptive traits related to aridity: pronounced leaf succulence with high volume-to-surface ratios, thick waxy cuticle, low stomatal density, smooth xeromorphic epidermis or covering of reflective papillae/hairs, compact growth form reducing the transpiring surface, shallow ‘rectifier-type’ roots efficiently capturing light rainfall, and natural vegetative reproduction through stem or leaf cuttings. Species in Clade C of Bruyns et al. (2019), which constitute the greatest diversification within the genus, show a marked trend toward increased succulence, leaf reduction and dense epidermal coverings (papillae, hairs, pruinosity), associated with a base chromosome number of x = 7. Species of Clades A and B, often with softer, flatter leaves, have a base number of x = 8 with frequent polyploidy.

Infrageneric Classification and Species List

The infrageneric classification presented below follows the system of Tölken (1977, 1985), which recognises two subgenera and 20 sections. Phylogenetic remarks integrate the molecular results of Bruyns et al. (2019). The species list is based on Plants of the World Online (Kew, December 2024, 216 accepted species). For each section, the most representative species are listed; a supplementary list of species not assigned to a specific section in the consulted literature appears at the end of this chapter.

Subgenus Crassula

Subgenus Crassula sensu Tölken comprises perennial species with pentamerous flowers whose carpels contain numerous ovules arranged in several rows. According to Tölken (1985), this subgenus includes 11 sections. It broadly corresponds to Clades B and C of Bruyns et al. (2019). It is here that the greatest recent diversification of the genus is found, concentrated in the GCFR.

Section Crassula

Section Crassula (type section of the genus) includes the best-known shrubby and sub-shrubby species, characterised by woody stems, fleshy opposite-decussate leaves and terminal thyrse or compound cyme inflorescences. This section contains the most widely cultivated plants in the genus, notably Crassula ovata (Mill.) Druce, the famous ‘jade plant’, and Crassula arborescens (Mill.) Willd., the ‘silver jade plant’. These species can form small trees reaching 6.5–10 ft (2–3 m) in their natural habitat, in the thickets of the Eastern Cape and KwaZulu-Natal. They share white to pinkish five-petalled flowers, winter flowering (in the Southern Hemisphere), and a remarkable ability to propagate from stem or leaf cuttings.

Representative species: 

Section Globulea (Haw.) Schönland

Section Globulea brings together dwarf species with highly fleshy leaves — often spherical, ovoid, or covered with dense papillae and hairs — forming compact cushions or basal rosettes. These are typical plants of the Succulent Karoo and Namaqualand, colonising rock crevices and quartzite slabs under extreme aridity. The epidermis is frequently pruinose, papillose or densely pubescent, providing protection against solar radiation and reducing cuticular water loss. The most sought-after species among collectors include Crassula mesembryanthemopsis Dinter, Crassula alstonii Marloth, and Crassula tecta Thunb. — miniature gems of the succulent world.

Representative species: 

  • Crassula alstonii Marloth, 
  • Crassula barbata Thunb., 
  • Crassula brevifolia Harv., 
  • Crassula compacta Schönland, 
  • Crassula corallina L.f., 
  • Crassula cotyledonis Thunb., 
  • Crassula deceptor Schönland & Baker f., 
  • Crassula deltoidea Thunb., 
  • Crassula elegans Schönland & Baker f., 
  • Crassula hemisphaerica Thunb., 
  • Crassula mesembryanthemopsis Dinter, 
  • Crassula mesembryanthoides (Haw.) D.Dietr., 
  • Crassula namaquensis Schönland & Baker f., 
  • Crassula rogersii Schönland, 
  • Crassula socialis Schönland, 
  • Crassula susannae Rauh & Friedrich, 
  • Crassula tecta Thunb., 
  • Crassula tomentosa Thunb.

Section Arta Schönland

Section Arta comprises species with a highly compact, columnar growth form, whose imbricate leaves form remarkable geometric columns. The columnar habit results from extreme internode reduction, with opposite leaf pairs overlapping tightly to form a nearly cylindrical or prismatic structure. These morphological adaptations minimise the surface area exposed to direct sunlight and reduce transpiration. The emblematic species of this section are Crassula columnaris L.f. and Crassula columella Marloth & Schönland, the latter forming silvery-grey columns no taller than 2–4 in (5–10 cm). Crassula pyramidalis Thunb. is another typical representative, with its flattened, four-angled stems. These plants are monocarpic or very rarely floriferous, as terminal flowering leads to the death of the stem.

Representative species: Crassula barklyi N.E.Br., Crassula columella Marloth & Schönland, Crassula columnaris L.f., Crassula pyramidalis Thunb.

Section Argyrophylla Toelken

Section Argyrophylla (from Greek argyros, silver, and phyllon, leaf) groups species with silvery leaves covered in a dense white or grey pubescence, or a thick coating of calcified papillae. These structures protect against the intense UV radiation of arid habitats in Namaqualand and Bushmanland. The molecular phylogenetic studies of Bruyns et al. (2019) showed that this section is not monophyletic: Crassula alstonii is phylogenetically closer to section Globulea than to Crassula tecta and Crassula mesembrianthemopsis, despite all three being placed in the same section by Tölken.

Representative species: Crassula pageae Toelken, Crassula pseudhemisphaerica Friedrich, Crassula sericea Schönland.

Section Rosulares Schönland

Section Rosulares brings together species forming flattened basal rosettes, often monocarpic, with leaves arranged in a tight spiral. The rosettes are frequently ciliate along their margins, the marginal hairs playing a role in capturing dew and coastal fog — a crucial water source in the semi-arid habitats of the Western Cape. After flowering, a spectacular scape emerges from the centre of the rosette, bearing white to cream flowers in dense cymes. The monocarpic (hapaxanthic) life cycle may extend over several years. Crassula orbicularis L. is the most widespread species of this section.

Representative species: Crassula orbicularis L., Crassula setulosa Harv., Crassula pubescens Thunb.

Section Petrogeton Toelken

Section Petrogeton (from Greek petros, rock, and geiton, neighbour) groups small, creeping or prostrate species that colonise rock outcrops and crevices. These are typical mat-forming plants of the Fynbos and Karoo biomes, forming dense carpets on quartzitic substrates. The leaves are minute and tightly imbricate along thread-like stems. Crassula muscosa L. (syn. Crassula lycopodioides Lam.) is the most cultivated species in this section, easily recognised by its stems resembling clubmosses or lizard tails. Crassula ericoides Haw., with leaves reminiscent of heather, is another typical representative.

Representative species: 

Section Fasciculares Schönland

Section Fasciculares groups species with a bushy or sub-shrubby habit whose leaves, often petiolate, are clustered in dense fascicles at the nodes. Inflorescences are typically fasciculate cymes. Crassula fascicularis Lam. is the type species, with lanceolate leaves and fragrant tubular flowers. Crassula coccinea L. is the most spectacular member, bearing clusters of scarlet-red flowers that earn it the nickname ‘red crassula’. This section is notable for the diversity of its floral forms, ranging from narrow tubular corollas (moth-pollinated) to broadly open corollas (bee-pollinated).

Representative species: 

  • Crassula coccinea L., 
  • Crassula fascicularis Lam., 
  • Crassula nudicaulis L., 
  • Crassula perfoliata L., 
  • Crassula rubricaulis Eckl. & Zeyh.

Section Campanulatae Schönland

Section Campanulatae (from Latin campanula, small bell) takes its name from the characteristic floral morphology of its members, whose petals are fused at the base to form a campanulate or tubular corolla. This section includes species of highly variable habit, from ephemeral annuals to robust perennials. Crassula umbella Jacq. is the most remarkable, with its umbellate inflorescence borne on a peduncle emerging from a pair of leaves fused into a cup (‘wine cup crassula’). It is one of the most sought-after species among collectors.

Representative species: 

Section Kalosanthes (Haw.) Toelken

Section Kalosanthes (from Greek kalos, beautiful, and anthos, flower) comprises species with particularly ornamental, often colourful, tubular flowers. Crassula perfoliata L. var. minor (Haw.) Toelken (often sold as Crassula falcata) is the best-known member, with its large coral-red inflorescences and sickle-shaped leaves. This section is phylogenetically close to section Fasciculares, and some authors merge them. Members display the largest and most colourful flowers in the genus, making them prized horticultural subjects.

Representative species: Crassula flava L., Crassula scabra L., Crassula vestita Thunb.

Section Montana Toelken

Section Montana groups herbaceous montane perennials found in high-altitude grasslands and on rock outcrops of the Drakensberg, Eastern Cape and KwaZulu-Natal. These species tolerate moderate frosts and benefit from more abundant summer rainfall than Karoo species. Crassula montana L.f. is a variable, widely distributed species with several subspecies. Crassula vaginata Eckl. & Zeyh. and Crassula natalensis Schönland are other representatives, growing in high-altitude mesic grasslands.

Representative species: Crassula glomerata P.J.Bergius, Crassula montana L.f., Crassula natalensis Schönland, Crassula vaginata Eckl. & Zeyh.

Section Subaphyllae Schönland

Section Subaphyllae (from Latin sub, almost, and aphyllus, leafless) groups species whose leaves are greatly reduced or virtually absent at maturity. The succulent stems become the primary photosynthetic organ. Crassula subaphylla (Eckl. & Zeyh.) Harv. and Crassula aphylla Schönland & Baker f. illustrate this evolutionary trend toward leaf reduction — an adaptation to the extreme aridity of the Succulent Karoo and Richtersveld.

Representative species: Crassula aphylla Schönland & Baker f., Crassula subaphylla (Eckl. & Zeyh.) Harv.

Subgenus Disporocarpa Toelken

Subgenus Disporocarpa (from Greek di, two, sporos, seed, and karpos, fruit) groups species whose carpels contain only two ovules arranged in a single row. This subgenus includes 9 sections according to Tölken (1985). Molecular analyses suggest it may be paraphyletic, but data remain insufficient for a full reorganisation. It corresponds mainly to Clade A of Bruyns et al. (2019). Many of its members are annuals or ephemeral perennials with cosmopolitan distributions.

Section Helophytum (Eckl. & Zeyh.) Endl.

Section Helophytum (from Greek helos, marsh, and phyton, plant) is the largest section in subgenus Disporocarpa. It groups small, often annual or ephemeral, herbaceous species with thin, barely succulent leaves. Many are ephemeral annuals germinating after rains in semi-arid areas. Some species colonise seasonally wet habitats, riverbanks and temporarily flooded clay soils. Crassula decumbens Thunb. and Crassula thunbergiana Schult. are typical representatives. Several species in this section have a cosmopolitan distribution and are considered adventive or invasive outside their natural range, notably Crassula helmsii (Kirk) Cockayne, an aquatic species native to Australasia that has become invasive in Europe.

Representative species: Crassula alba Forssk., Crassula campestris (Eckl. & Zeyh.) Endl., Crassula colorata (Nees) Ostenf., Crassula decumbens Thunb., Crassula dichotoma L., Crassula glomerata P.J.Bergius, Crassula inanis Thunb., Crassula natans Thunb., Crassula nemorosa (Eckl. & Zeyh.) Endl., Crassula pellucida L., Crassula sediflora (Eckl. & Zeyh.) Endl., Crassula thunbergiana Schult., Crassula vaillantii (Willd.) Roth.

Section Tillaea (L.) Endl.

Section Tillaea corresponds to the former genus Tillaea L., now included in Crassula following the molecular work of Mort et al. (2009). These are minute annual plants, often only a few centimetres tall, with opposite filiform leaves and solitary or small-clustered tetramerous flowers. Although morphologically very different from the succulent Crassula species of southern Africa, chloroplast DNA data firmly place Tillaea within Crassula. Crassula tillaea Lest.-Garl. is a circum-Mediterranean species found in southern France — the only Crassula species native to mainland Europe. Crassula aquatica (L.) Schönland is a circumboreal aquatic species.

Representative species: Crassula aquatica (L.) Schönland, Crassula closiana (Gay) Reiche, Crassula connata (Ruiz & Pav.) A.Berger, Crassula drummondii (Torr. & A.Gray) Fedde, Crassula helmsii (Kirk) Cockayne, Crassula longipes (Rose) M.Bywater & Wickens, Crassula moschata G.Forst., Crassula peduncularis (Sm.) Cambess., Crassula sieberiana (Schult. & Schult.f.) Druce, Crassula tillaea Lest.-Garl., Crassula viridis (S.Watson) M.Bywater & Wickens.

Section Dinacria (Harv.) Toelken

Section Dinacria comprises a small number of annual species with pedicellate flowers, characterised by foliaceous bracts and seeds with distinctive ornamentation. These are ephemeral annuals of the Fynbos, Renosterveld and rocky outcrops, germinating after winter rains. Crassula sebaeoides (Eckl. & Zeyh.) Toelken is a typical representative.

Representative species: Crassula sebaeoides (Eckl. & Zeyh.) Toelken.

Section Disporocarpa (Toelken)

The type section of subgenus Disporocarpa sensu stricto groups small annual or ephemeral perennial species, with seeds arranged in two rows per carpel (hence the name Disporocarpa, ‘two-seeded fruit’). This section includes several species from tropical Africa, East Africa and Madagascar, constituting the rare representatives of the genus outside southern Africa. Crassula volkensii Engl., Crassula granvikii Mildbr. and Crassula ankaratrensis Desc. are East African and Malagasy species in this section.

Representative species: Crassula alticola R.Fern., Crassula ankaratrensis Desc., Crassula bevilanensis Desc., Crassula granvikii Mildbr., Crassula humbertii Desc., Crassula schimperi Fisch. & C.A.Mey., Crassula volkensii Engl.

Species Not Assigned to a Section in the Consulted Literature

The following species, accepted by POWO (2024), have not been formally assigned to a section in the publications consulted, or their sectional placement is the subject of ongoing taxonomic discussion. Many are recently described species (van Jaarsveld, Jacobsen, Smith & Crouch) or extralimital species whose infrageneric placement requires additional molecular data.

Crassula acinaciformis Schinz, Crassula alata (Viv.) A.Berger, Crassula alcicornis Schönland, Crassula alpestris L.f., Crassula alsinoides (Hook.f.) Engl., Crassula ammophila Toelken, Crassula anso-lerouxiae van Jaarsv., Crassula aurusbergensis G.Will., Crassula ausensis Hutchison, Crassula badspoortensis van Jaarsv., Crassula basaltica Brullo & Siracusa, Crassula bergioides Harv., Crassula biplanata Haw., Crassula brachystachya Toelken, Crassula calcarea N.H.G.Jacobsen, Crassula capensis (L.) Baill., Crassula clavata N.E.Br., Crassula colligata Toelken, Crassula congesta N.E.Br., Crassula cooperi Regel, Crassula cordata Thunb., Crassula cordifolia Baker, Crassula crassifolia N.H.G.Jacobsen, Crassula cremnophila van Jaarsv. & A.E.van Wyk, Crassula crenulata Thunb., Crassula cymbiformis Toelken, Crassula cymosa P.J.Bergius, Crassula decidua Schönland, Crassula dentata Thunb., Crassula dependens Bolus, Crassula depressa (Eckl. & Zeyh.) Toelken, Crassula dodii Schönland & Baker f., Crassula elatinoides (Eckl. & Zeyh.) Friedrich, Crassula elsieae Toelken, Crassula exilis Harv., Crassula exserta (Reader) Ostenf., Crassula extrorsa Toelken, Crassula fallax Friedrich, Crassula filiformis (Eckl. & Zeyh.) D.Dietr., Crassula flanaganii Schönland & Baker f., Crassula floribunda (Friedrich ex Toelken) N.R.Crouch, Gideon F.Sm. & D.Styles, Crassula foveata van Jaarsv., Crassula fragarioides van Jaarsv. & Helme, Crassula fusca Herre, Crassula garibina Marloth & Schönland, Crassula gemmifera Friedrich, Crassula globularioides Britten, Crassula grammanthoides (Schönland) Toelken, Crassula grisea Schönland, Crassula hirsuta Schönland & Baker f., Crassula hirtipes Harv., Crassula hunua A.P.Druce, Crassula inandensis Schönland & Baker f., Crassula intermedia Schönland, Crassula karroica N.H.G.Jacobsen, Crassula kirkii (Allan) A.P.Druce & Given, Crassula lanuginosa Harv., Crassula lasiantha E.Mey. ex Harv., Crassula latibracteata Toelken, Crassula leachii R.Fern., Crassula macowaniana Schönland & Baker f., Crassula manaia A.P.Druce & Sykes, Crassula maputensis R.Fern., Crassula × marchandii Friedrich, Crassula mataikona A.P.Druce, Crassula micans Vahl ex Baill., Crassula minuta Toelken, Crassula minutissima Skottsb., Crassula mollis Thunb., Crassula moniliformis N.H.G.Jacobsen, Crassula morrumbalensis R.Fern., Crassula × mortii Gideon F.Sm. & N.R.Crouch, Crassula multicaulis (Petrie) A.P.Druce & Given, Crassula multiceps Harv., Crassula multiflora Schönland & Baker f., Crassula muricata Thunb., Crassula nanshanchunensis (S.S.Ying) S.S.Ying, Crassula nodulosa Schönland, Crassula numaisensis Friedrich, Crassula nyikensis Baker, Crassula oblanceolata Schönland & Baker f., Crassula obovata Haw., Crassula obtusa Haw., Crassula pallens Schönland & Baker f., Crassula papillosa Schönland & Baker f., Crassula peculiaris (Toelken) Toelken & Wickens, Crassula peploides Harv., Crassula phascoides (Griseb.) M.Bywater, Crassula planifolia Schönland, Crassula plegmatoides Friedrich, Crassula pruinosa L., Crassula purcellii Schönland, Crassula pustulata Toelken, Crassula qoatlhambensis Hargr., Crassula quadrifaria N.Jacobsen, Crassula radicans (Haw.) D.Dietr., Crassula rattrayi Diels ex Schönland & Baker f., Crassula rhodesica (Merxm.) Wickens & M.Bywater, Crassula roggeveldii Schönland, Crassula ruamahanga A.P.Druce, Crassula rudolfii Schönland & Baker f., Crassula saginoides (Maxim.) M.Bywater & Wickens, Crassula sandrae N.H.G.Jacobsen, Crassula saxifraga Harv., Crassula × scabrella Haw., Crassula × serpentaria Schönland, Crassula simulans Schönland, Crassula sinclairii (Hook.f.) A.P.Druce & Given, Crassula sladenii Schönland, Crassula smithii van Jaarsv., D.G.A.Styles & G.McDonald, Crassula solieri (Gay) F.Meigen, Crassula southii Schönland, Crassula streyi Toelken, Crassula stylesii Gideon F.Sm. & N.R.Crouch, Crassula subacaulis Schönland & Baker f., Crassula subulata L., Crassula tabularis Dinter, Crassula tenuicaulis Schönland, Crassula tenuipedicellata Schönland & Baker f., Crassula tetramera (Toelken) A.P.Druce & Sykes, Crassula tuberella Toelken, Crassula umbraticola N.E.Br., Crassula venezuelensis (Steyerm.) M.Bywater & Wickens, Crassula werneri N.H.G.Jacobsen, Crassula whiteheadii Harv., Crassula zombensis Baker f.

Major Botanical Collections for Crassulaceae

The principal herbarium and living collections of Crassulaceae, and Crassula in particular, include the following:

Bolus Herbarium (BOL), University of Cape Town, South Africa. Historic herbarium founded in 1865, housing Tölken’s type specimens. The Crassula collection has been entirely digitised. It is the world reference collection for the genus.

Compton Herbarium (NBG), Kirstenbosch, SANBI, South Africa. Housed at Kirstenbosch National Botanical Garden, this herbarium of 320,000 specimens focuses on the winter-rainfall Cape flora. Kirstenbosch’s living collections include numerous Crassula species in the conservatory and succulent gardens.

National Herbarium of South Africa (PRE), Pretoria, SANBI. The largest herbarium in Africa, with over 1.2 million specimens, including important Crassulaceae collections from across southern Africa.

Royal Botanic Gardens, Kew (K), United Kingdom. Major historical collections of southern African Crassulaceae, including specimens by Harvey, Thunberg and Marloth. Kew also manages the POWO (Plants of the World Online) database, the global taxonomic reference.

Sukkulenten-Sammlung Zürich, Switzerland. One of the world’s most important living collections of succulent plants, with a rich holding of Crassula and other Crassulaceae.

Botanischer Garten Berlin-Dahlem, Germany. Historic collections of African succulents, with an herbarium (B) containing types by Dinter, Schönland and Berger.

Jardin Exotique de Monaco. Remarkable living collection of Crassulaceae, including South African Crassula species cultivated under Mediterranean conditions.

Desert Botanical Garden, Phoenix, Arizona, USA. Living collections of succulents from around the world, with significant Crassulaceae representation.

Muséum National d’Histoire Naturelle, Paris (P), France. Historic herbarium with specimens by Lamarck and Thunberg, as well as collections from southern Africa and Madagascar (Humbert, Descoings).

Authority Sites and Online Resources

Plants of the World Online (POWO) — Royal Botanic Gardens, Kew
https://powo.science.kew.org/taxon/30014394-2

International Crassulaceae Network (ICN) — Margrit Bischofberger
https://www.crassulaceae.ch/

PlantZAfrica — South African National Biodiversity Institute (SANBI)
https://pza.sanbi.org/

JSTOR Global Plants
https://plants.jstor.org/

World Flora Online (WFO)
https://www.worldfloraonline.org/

GBIF — Global Biodiversity Information Facility
https://www.gbif.org/

iNaturalist — Crassula observations
https://www.inaturalist.org/taxa/57017-Crassula

LLIFLE — Encyclopedia of Living Forms
https://www.llifle.com/Encyclopedia/…

World of Succulents — Crassula
https://worldofsucculents.com/genera/crassula/

Red List of South African Plants (SANBI)
https://redlist.sanbi.org/

Biodiversity Heritage Library (BHL)
https://www.biodiversitylibrary.org/

Tropicos — Missouri Botanical Garden
https://www.tropicos.org/

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