Family Crassulaceae

The Crassulaceae — commonly known as the stonecrop family or orpine family — form one of the largest and most diverse families of succulent plants on Earth. From the ubiquitous Crassula ovata on a kitchen windowsill to the frost-hardy Sempervivum tectorum carpeting alpine rooftops, this single family spans an astonishing range of forms, sizes, and climates. With approximately 35 genera and over 1,400 accepted species, the Crassulaceae dominate the succulent hobby and the horticultural trade worldwide.

For growers, the family offers something rare: a lineage where nearly every member shares the same core cultural requirements — excellent drainage, moderate to bright light, and restrained watering — yet delivers an almost infinite palette of leaf shapes, rosette architectures, growth habits, and flower colours. Whether you grow a single jade plant or maintain a collection spanning dozens of genera, understanding the Crassulaceae as a family provides the botanical foundation that transforms guesswork into confident cultivation.

Quick Facts

Attribute	Details
Family	Crassulaceae J.St.-Hil. (1805)
Order	Saxifragales
Number of genera	~35 (depending on taxonomic treatment)
Number of species	~1,400 accepted species
Distribution	Cosmopolitan — every continent except Antarctica; diversity centres in southern Africa, Mexico, Macaronesia, and temperate Eurasia
Type genus	Crassula L.
Key synapomorphies	Succulent leaves or stems; CAM or facultative CAM photosynthesis; obdiplostemonous flowers (stamens in two whorls); free or slightly fused carpels
Hardiness range	USDA 3 to USDA 12 depending on genus (from alpine Sempervivum to tropical Kalanchoe)
Common names	Stonecrop family, orpine family

Taxonomy and Classification

Position within the angiosperms

The Crassulaceae belong to the order Saxifragales, a clade of core eudicots that also includes the Saxifragaceae (saxifrages), Haloragaceae (water milfoils), and Grossulariaceae (currants and gooseberries). Molecular phylogenetic studies since the early 2000s have firmly placed the Crassulaceae as a monophyletic group within this order, although the exact sister relationships remain debated. The family was first described by Jean Henri Jaume Saint-Hilaire in 1805, with Crassula as the type genus.

Subfamilies

Modern molecular phylogenetics, building on the foundational work of ‘t Hart (1995) and Mort et al. (2001), generally recognises three subfamilies within the Crassulaceae. While some authors propose alternative arrangements, the tripartite division provides a practical framework for understanding relationships within the family:

Subfamily Crassuloideae — This basal lineage contains a single genus, Crassula, with approximately 200 species centred on southern Africa. Despite representing only one genus, the Crassuloideae display remarkable morphological diversity, from dwarf column-forming species barely 3 cm tall to tree-like shrubs exceeding 3 m. The former genus Tillaea, once treated separately for its diminutive annual members, is now subsumed within Crassula.

Subfamily Kalanchoideae — A predominantly African and Malagasy lineage containing approximately four genera: Kalanchoe (including the former Bryophyllum), Cotyledon, Tylecodon, and Adromischus. Many members are winter-growing or have distinctive deciduous habits. Tylecodon, segregated from Cotyledon by Toelken in 1978, is notable for its summer-deciduous, caudiciform species — several of which are highly toxic to livestock.

Subfamily Sempervivoideae — The largest and most horticulturally significant subdivision, encompassing roughly 30 genera and over 1,000 species. This subfamily absorbs the former Sedoideae and Echeverioideae of older classifications. It includes several major tribes:

• Tribe Semperviveae: Sempervivum, Jovibarba, Rosularia, Prometheum, Monanthes — mostly European and Central Asian rosette formers, often extremely cold-hardy.
• Tribe Aeonieae: Aeonium, Aichryson, Greenovia (now usually included in Aeonium) — centred on the Canary Islands and Macaronesia, with a winter-growing rhythm and spectacular rosette diversity.
• Tribe Sedeae: Sedum (sensu lato), Hylotelephium, Rhodiola, Phedimus, Petrosedum, Rosularia — the largest tribe, cosmopolitan, spanning from alpine tundra to subtropical rocks. The genus Sedum in the traditional sense is polyphyletic, and ongoing revisions continue to segregate new genera.
• Tribe Echeverieae (Acre clade): Echeveria, Pachyphytum, Graptopetalum, Dudleya, Lenophyllum, Villadia, Thompsonella — almost exclusively New World, centred on Mexico. This tribe is the backbone of the modern succulent ornamental industry, with thousands of cultivars and intergeneric hybrids (× Graptoveria, × Pachyveria, × Graptosedum, etc.).

A family in taxonomic flux

Crassulaceae taxonomy is notoriously unstable. The genus Sedum, historically a catch-all for stonecrop-like plants, has been progressively dismembered into smaller genera (Hylotelephium, Phedimus, Petrosedum, Rhodiola), and this process is not yet complete. Similarly, Bryophyllum has been folded into Kalanchoe, and Greenovia into Aeonium, though many growers and retailers still use the old names. For authoritative nomenclature, Plants of the World Online (POWO, maintained by Kew) remains the recommended reference.

Morphology

Growth habit

The Crassulaceae exhibit virtually every succulent growth form. Rosette-forming species dominate in Echeveria, Sempervivum, Aeonium, and Graptopetalum. Shrubby and tree-like habits appear in Crassula ovata, Kalanchoe beharensis, and Cotyledon orbiculata. Pendant or trailing forms occur in Crassula pellucida, Sedum morganianum, and Ceropegia-like creeping Crassula species. Columnar stacking of tightly appressed leaves is found in Crassula pyramidalis, Crassula columnaris, and Crassula deceptor. Finally, caudiciform growth — with a thickened basal stem and deciduous branches — characterises many Tylecodon and certain Adromischus.

Leaves

Succulent leaves are the defining feature of the family. The mesophyll is packed with large, water-storing parenchyma cells. Leaf surfaces may be smooth, papillose, hairy, or coated in a waxy epicuticular bloom (farina), which serves as UV protection and reduces transpiration. Leaf arrangement is typically opposite-decussate in Crassula, alternate-spiral in Sedum, and rosulate in Echeveria and Sempervivum. Leaf margins may be entire, crenate, or ciliate. Coloration ranges from green through grey-blue, purple, red, and near-black, often intensifying under drought or cold stress.

Flowers

Crassulaceae flowers are typically actinomorphic (radially symmetrical), with parts in fours or fives. The stamens are obdiplostemonous — arranged in two whorls, with the outer whorl opposite the petals rather than alternating with them, a characteristic shared with few other angiosperm families. The carpels are free or only slightly fused at the base, each maturing into a follicle containing numerous tiny seeds. Pollination is primarily entomophilous (insect-mediated). Inflorescences vary enormously: compact cymes in Crassula, terminal panicles in Aeonium, pendant bell-shaped clusters in Kalanchoe, and flat-topped corymbs in Hylotelephium.

CAM photosynthesis

The Crassulaceae gave their name to Crassulacean Acid Metabolism (CAM) — the water-conserving photosynthetic pathway in which stomata open at night to fix CO₂ as malic acid, then close during the day while the stored acid is decarboxylated and fed into the Calvin cycle. Not all Crassulaceae are obligate CAM plants; many Sedum and Sempervivum species use facultative CAM, switching between C₃ and CAM depending on water availability and temperature. This metabolic flexibility is one reason the family has colonised such a wide range of habitats, from arid southern African karoo to seasonally dry European cliffs and even humid tropical forests.

Distribution and Habitat

The Crassulaceae are found on every continent except Antarctica, but their diversity is concentrated in several well-defined hotspots:

Southern Africa — The single richest region for the family. The Greater Cape Floristic Region and the Succulent Karoo harbour the majority of Crassula species (over 150), along with most Adromischus, Cotyledon, and Tylecodon. Rainfall seasonality (winter-wet in the west, summer-wet in the east) drives ecological and morphological divergence within genera.

Mexico and the southwestern United States — The primary radiation centre for the Echeverieae tribe. Echeveria (~150 species), Pachyphytum, Graptopetalum, Villadia, and Dudleya are overwhelmingly Mexican endemics, often restricted to specific mountain ranges or canyon systems. Cloud forests, semi-arid canyons, and vertical cliff faces are typical habitats.

Macaronesia (Canary Islands, Madeira, Cape Verde) — The centre of diversity for Aeonium (~35 species) and Monanthes. Volcanic substrates, altitude-driven moisture gradients, and island isolation have produced extraordinary speciation.

Temperate and alpine Eurasia — Home to Sempervivum, Jovibarba, Rosularia, Rhodiola, and the northern Sedum radiation. Species grow in rock crevices, scree slopes, and alpine meadows from the Pyrenees to the Himalayas. Some, like Rhodiola rosea, extend into the Arctic.

Madagascar and East Africa — The main centre for Kalanchoe (over 100 species on Madagascar alone), with secondary diversity in tropical East Africa and the Arabian Peninsula.

Habitats across the family are predominantly rocky, well-drained, and exposed to high light. Many Crassulaceae are lithophytes or chasmophytes, growing in rock crevices where competition from grasses and shrubs is minimal. Even in temperate regions, the family gravitates toward walls, cliffs, green roofs, and thin soils where drainage is assured.

Complete List of Genera

Plants of the World Online (POWO, Kew) currently accepts 39 genera within the Crassulaceae. These are distributed across three subfamilies defined by molecular phylogenetics (Thiede & Eggli, 2007; Messerschmid et al., 2020). The classification below follows the subfamilial and tribal framework of Thiede & Eggli (2007), updated to reflect genera added to POWO since that treatment — notably several recent Mexican segregates described by Vázquez-García and colleagues. Genus-level taxonomy in the Crassulaceae remains fluid; readers should consult POWO for the latest accepted names.

Subfamily Crassuloideae — The Crassula lineage

The Crassuloideae represent the earliest-diverging subfamily within the Crassulaceae. The clade is defined by a single synapomorphy unique in the family: haplostemony, meaning each flower possesses a single whorl of stamens equal in number to the petals (typically five), rather than the two whorls (obdiplostemony) found in all other Crassulaceae. Leaves are consistently opposite and decussate, with paired hydathodes — water-excreting glands visible as marginal dots. The subfamily is overwhelmingly southern African in origin, though a handful of diminutive, often annual species (formerly segregated as Tillaea) have achieved near-cosmopolitan distribution. Despite comprising a single genus, the Crassuloideae display a remarkable spectrum of growth forms, from aquatic annuals barely 1 cm tall to tree-like shrubs exceeding 3 m.

• Crassula L. — ~200 species. Southern Africa, with a secondary cosmopolitan range for small annual species. Includes the former genera Tillaea, Bulliarda, and Helophytum. Growth forms span aquatic annuals, columnar miniatures, creeping mats, shrubs, and small trees. Crassula ovata (jade plant) is the most widely cultivated species in the entire family.

Subfamily Kalanchoideae — The Kalanchoe lineage

The Kalanchoideae form the sister group to the Sempervivoideae. The subfamily is characterised by sympetalous (fused-petal) flowers — a feature that historically led to all four genera being lumped under a broadly defined Cotyledon before modern taxonomy clarified their distinctness. All four genera share leaves with a single apical or subapical hydathode and seeds with a costate (ribbed) testa. The Kalanchoideae are predominantly southern African, with Kalanchoe as the exception — its centre of diversity is Madagascar, from where it radiates into tropical Africa and Southeast Asia. Several species are caudiciform or deciduous, and toxicity to livestock is notable in Tylecodon and Cotyledon.

• Adromischus Lem. — ~28 species. Endemic to southern Africa (South Africa, Namibia). Compact plants with uniquely shaped, often spotted or textured leaves. Winter-growing. Popular collector’s genus requiring sharp drainage. USDA zones 10–11.
• Cotyledon L. — ~15 species. Southern and East Africa. Shrubby succulents with opposite leaves and pendant, bell-shaped flowers. Cotyledon orbiculata is the most widely cultivated species. Some species are toxic. USDA zones 9b–11.
• Kalanchoe Adans. — ~150 species. Madagascar (primary centre), tropical Africa, tropical Asia, and the Arabian Peninsula. Includes the former genus Bryophyllum (viviparous species producing plantlets on leaf margins). Growth forms range from small herbs to tree-like species (Kalanchoe beharensis). Kalanchoe blossfeldiana is one of the world’s most important potted flower crops. Frost-tender (USDA zones 10–12).
• Tylecodon Toelken — ~46 species. Southern Africa (mainly western South Africa, Namibia). Segregated from Cotyledon by Toelken in 1978. Distinctive caudiciform habit with tortuous, peeling bark and deciduous leaves shed in summer. Winter-growing, strictly summer-dormant. Several species are highly toxic to livestock (bufadienolides), causing the condition known as “krimpsiekte” in South Africa. USDA zones 10–11.

Subfamily Sempervivoideae — The largest and most diverse lineage

The Sempervivoideae encompass roughly 30 genera and over 1,000 species, making them the largest subdivision of the family by far. This subfamily absorbs the former “Sedoideae” of older classifications (Sempervivoideae has taxonomic priority). All members share obdiplostemonous flowers with two whorls of stamens. The subfamily is divided into five tribes, which in turn contain several well-supported molecular clades. The Sempervivoideae are predominantly Northern Hemisphere in distribution, with a major secondary radiation in Mexico and Central America. They include the most cold-hardy succulents on Earth (Sempervivum, Rhodiola) as well as frost-tender tropical genera. The genus Sedum — by far the largest in the family — is scattered across multiple tribes and clades, and is now universally acknowledged to be polyphyletic.

Tribe Telephieae

A predominantly East Asian lineage with a base chromosome number of x = 12. The tribe includes familiar autumn-flowering border plants (the “tall sedums” of horticulture), as well as several small genera of rosette-forming or column-forming alpines from China, Mongolia, and Siberia. Many species are deciduous and fully cold-hardy.

• Hylotelephium H.Ohba — ~30 species. Temperate Eurasia and North America. Segregated from Sedum by Ohba in 1977. Herbaceous perennials with flat-topped flower heads, blooming in autumn — the classic “border sedums” of European gardens (Hylotelephium spectabile, Hylotelephium telephium). Fully hardy (USDA zones 3–9).
• Kungia K.T.Fu — 2 species. Southwestern China (Sichuan, Yunnan). Segregated from Orostachys. Rare rosette-forming alpine plants. Rarely cultivated.
• Meterostachys Nakai — 1 species (Meterostachys sikokianus). Japan and Korea. Monotypic genus of biennial or perennial rosettes. Extremely rare in cultivation.
• Orostachys Fisch. — ~15 species. Central and East Asia (China, Mongolia, Siberia, Korea, Japan). “Dunce caps” — monocarpic rosettes producing a distinctive conical terminal inflorescence. Very cold-hardy, growing in rock crevices at high elevations. USDA zones 3–7.
• Sinocrassula A.Berger — ~10 species. China (mainly southwestern provinces), Myanmar. Dense rosettes of small, dark-coloured leaves, sometimes nearly black. Monocarpic. Rarely cultivated outside specialist collections.

Tribe Umbiliceae

A tribe centred on temperate Eurasia, containing both alpine cushion plants and woodland succulents. The tribe includes the Rhodiola clade — a predominantly arctic-alpine group — and the navelwort lineage (Umbilicus). Chromosome numbers are notably elevated in some genera (x = 16 in Phedimus, x = 24 in Umbilicus), likely reflecting ancient polyploidy events.

• Chiastophyllum (Ledeb.) A.Berger — 1 species (Chiastophyllum oppositifolium). Caucasus (Georgia, western Russia). A shade-tolerant woodland succulent with opposite, rounded leaves and graceful pendant racemes of yellow flowers — the “lamb’s tail” of horticulture. Hardy to USDA zone 5.
• Phedimus Raf. — ~20 species. East Asia, extending into eastern Europe. Segregated from Sedum. Creeping to ascending herbs with flat, toothed leaves. Several species are widely used as ornamental ground covers (Phedimus spurius, sold as “Sedum spurium” in the trade). Hardy (USDA zones 3–8).
• Pseudosedum (Boiss.) A.Berger — ~5 species. Iran, Central Asia. Small, tuberous-rooted perennials from dry mountainous regions. Rarely cultivated. Related to Rhodiola.
• Rhodiola L. — ~60 species. Arctic and alpine regions of Eurasia, western North America. Thick rhizomatous rootstocks and fleshy, often deciduous aerial stems. Rhodiola rosea (golden root, roseroot) has been used for centuries in Scandinavian, Russian, and Tibetan traditional medicine as an adaptogen. Among the most cold-tolerant succulents, withstanding temperatures well below –40 °C (USDA zones 1–7).
• Umbilicus DC. — ~5 species. Mediterranean Basin, western Europe, Macaronesia. “Navelworts” or “pennyworts” — distinctive round peltate leaves with a central depression. Shade-tolerant; grows in wall crevices and shaded rock faces. Umbilicus rupestris is common throughout Atlantic Europe. Hardy to USDA zone 7.

Tribe Semperviveae

A predominantly European and Central Asian tribe of rosette-forming succulents. The tribe includes some of the hardiest succulents on Earth, many of which grow in exposed alpine environments above the treeline. Rosettes are typically monocarpic at the individual level but offset freely, forming clonal mats that persist indefinitely. The tribe is the foundation of the alpine trough and rock garden tradition in European horticulture.

• Afrovivella A.Berger — 1 species (Afrovivella semiensis). Ethiopian Highlands (Simien Mountains). An isolated relict, probably representing the southernmost natural outpost of the Semperviveae. Extremely rare, both in the wild and in cultivation.
• Hypagophytum A.Berger — 1 species (Hypagophytum abyssinicum). Ethiopia and Eritrea. Small rosette-forming plants from rocky habitats. Rarely cultivated.
• Prometheum (A.Berger) H.Ohba — ~2 species. Turkey, Iran, Caucasus. Small annual or biennial rosettes formerly included in Sedum or Rosularia. Monocarpic, producing offsets. Alpine rock crevices.
• Rosularia (DC.) Stapf — ~30 species. Turkey, Iran, Central Asia, Himalayas. Small rosette-forming plants resembling miniature Sempervivum, but with important floral differences (petals usually fused at the base). Rock crevices and scree slopes. Increasingly popular with alpine growers. Hardy to USDA zone 5–7.
• Sempervivum L. — ~40 species. Mountains of Europe (from the Pyrenees to the Caucasus), Turkey. “Houseleeks” or “hen-and-chicks” — among the hardiest succulents on Earth, tolerating temperatures below –30 °C (USDA zones 3–8). Monocarpic rosettes that offset prolifically. Over 7,000 named cultivars exist. Historically planted on rooftops in Europe (the specific epithet of Sempervivum tectorum means “of the roofs”). Excellent for rock gardens, alpine troughs, walls, and green roofs.

Tribe Aeonieae

A predominantly Macaronesian tribe (Canary Islands, Madeira, Cape Verde), with secondary diversity in East Africa. The tribe is defined by a distinctive winter-growing rhythm: vegetative growth occurs during the cool, moist season, and plants often go partially dormant and lose older leaves during hot, dry summers. Speciation on volcanic islands has produced remarkable diversity within small geographic areas.

• Aeonium Webb & Berthel. — ~35 species. Canary Islands (primary centre), Madeira, Cape Verde, Morocco, East Africa. Includes the former genus Greenovia. Branching shrubs bearing terminal rosettes of varying size, from 2 cm (Aeonium sedifolium) to over 50 cm (Aeonium canariense). Many rosettes are monocarpic but the plant survives via branching. Winter-growing, summer-dormant. Excellent in Mediterranean climates. Aeonium arboreum ‘Zwartkop’ (black-purple rosettes) is one of the most popular cultivated succulents worldwide. USDA zones 9b–11.
• Aichryson Webb & Berthel. — ~15 species. Canary Islands, Madeira, Azores, Morocco. Small, often hairy, short-lived herbs or subshrubs with soft, rounded leaves. “Tree of love” in the nursery trade. Less commonly cultivated than Aeonium. USDA zones 10–11.
• Monanthes Haw. — ~10 species. Canary Islands, Madeira, Savage Islands. Diminutive cushion-forming plants, some barely 2 cm across. Flowers with parts in 6–8 (unusual for Crassulaceae). Collector’s genus for alpine house culture.

Tribe Sedeae

The largest tribe of the Sempervivoideae, containing approximately 640 species. Molecular phylogenetics consistently recovers two major sister clades within Sedeae: the Leucosedum clade (predominantly Old World) and the Acre clade (predominantly New World, plus a substantial Eurasian component). The genus Sedum in its traditional, Linnaean sense is scattered across both clades and is universally acknowledged as polyphyletic — one of the most problematic taxonomic issues in all of succulent botany. Ongoing revisions continue to refine generic boundaries.

Leucosedum clade — A mainly Old World lineage centred on the Mediterranean, Macaronesia, and Africa, containing many of the “classical” European stonecrops.

• Perrierosedum (A.Berger) H.Ohba — 1 species (Perrierosedum madagascariense). Madagascar. A poorly known monotypic genus whose phylogenetic position remains uncertain; tentatively placed near the Leucosedum clade.
• Petrosedum Grulich — ~10 species. Europe, Mediterranean Basin. Segregated from Sedum. Includes familiar European rock stonecrops: Petrosedum sediforme (= Sedum sediforme), Petrosedum rupestre (= Sedum rupestre). Widely used in green roofs and rock gardens. Hardy (USDA zones 5–9).
• Pistorinia DC. — ~3 species. Iberian Peninsula, Morocco. Small annuals or biennials from dry rocky habitats. Rarely cultivated.

Acre clade — A highly diverse lineage with a major radiation in Mexico and the Americas (the Echeverieae complex), plus widespread Eurasian Sedum species. This clade is the backbone of the modern ornamental succulent industry, generating thousands of cultivars and intergeneric hybrids.

• Chaloupkaea Niederle — Recently described genus. Mexico. Segregated from Echeveria based on molecular and morphological evidence. Placement and species count still being refined.
• Chazaroa A.Vázquez, Padilla-Lepe & Rosales — Recently described genus. Mexico (Jalisco region). Another segregate from the Echeveria/Sedum complex. Accepted by POWO but not yet widely adopted in horticultural references.
• Cremnophila Rose — 2 species. Mexico (Oaxaca, Puebla). Cliff-dwelling rosette plants with pendant inflorescences. Treated as a separate genus by POWO but included within Sedum by Thiede & Eggli (2007). Rare in cultivation.
• Dudleya Britton & Rose — ~45 species. Western United States (California, Arizona) and Baja California (Mexico). Chalky-white or grey-green rosettes growing on coastal cliffs and rocky inland slopes. Winter-growing, summer-dormant. Some species are critically endangered due to systematic illegal collection for the Asian succulent market. USDA zones 9–11.
• Echeveria DC. — ~150 species. Mexico (primary centre), Central America, northwestern South America. The most commercially important genus in the modern ornamental succulent trade. Rosette-forming plants with an extraordinary range of leaf shapes, colours, and textures. Thousands of cultivars and numerous intergeneric hybrids (× Graptoveria, × Pachyveria, × Sedeveria, etc.). Intolerant of sustained frost. USDA zones 9b–11.
• Graptopetalum Rose — ~20 species. Mexico, southwestern United States. “Ghost plants” — pale, pastel-toned rosettes with thick, farinose leaves. Parent of the popular × Graptoveria and × Graptosedum intergeneric hybrids. Easy to propagate from leaf cuttings. USDA zones 9–11.
• Jeronimoa A.Vázquez, Islas & Rosales — Recently described genus. Mexico. Segregated from the Echeveria/Sedum complex. Accepted by POWO; circumscription still being evaluated.
• Lenophyllum Rose — ~7 species. Texas (USA) and northeastern Mexico. Small, creeping or trailing plants with opposite, fleshy leaves. Easily propagated from individual leaves which detach readily. Rarely available in mainstream commerce.
• Pachyphytum Link, Klotzsch & Otto — ~20 species. Mexico. Thick, rounded, heavily farinose leaves often described as “sugarcoated.” Parent genus of the popular × Pachyveria hybrids with Echeveria. USDA zones 9b–11.
• Quetzalcoatlia A.Vázquez, Rosales & Padilla-Lepe — Recently described genus. Mexico. Yet another segregate from the Mexican Crassulaceae complex. Accepted by POWO but still under evaluation by the broader taxonomic community.
• Sedum L. — ~400–500 species (depending on circumscription). Cosmopolitan, mainly Northern Hemisphere. By far the largest genus in the family — and the most taxonomically problematic. Sedum as traditionally defined is polyphyletic, with species scattered across multiple clades in Sedeae. Ongoing revisions continue to segregate lineages into smaller, monophyletic genera (Petrosedum, Phedimus, Hylotelephium, Rhodiola, etc.), but the process is far from complete. In horticulture, Sedum encompasses green roof workhorses (Sedum album, Sedum acre), trailing houseplants (Sedum morganianum, burro’s tail), and alpine miniatures. Hardiness ranges from USDA zone 3 to USDA zone 11 depending on species.
• Thompsonella Britton & Rose — ~3 species. Mexico (Oaxaca, Puebla, Guerrero). Small rosette plants growing on limestone cliffs. Deciduous in the dry season. Rare in cultivation. Related to Echeveria and Lenophyllum.
• Villadia Rose — ~15 species. Mexico, Central America, Peru. Small herbs or subshrubs with alternate, cylindrical leaves and small flowers. Often found in rock crevices at middle to high elevations. Rarely cultivated outside specialist collections.

Cultivation — General Principles for the Family

Despite their diversity, most cultivated Crassulaceae share a common set of cultural requirements. Understanding these family-wide principles provides a reliable baseline, even though individual genera and species may require adjustments.

Substrate and drainage

Drainage is the single most important factor in Crassulaceae cultivation — more plants are lost to root rot from poor substrate than to any other cause. A well-draining mineral mix is essential. A standard starting recipe consists of roughly 60–70% mineral aggregate (pumice, perlite, lava rock, or coarse sand) and 30–40% organic matter (peat-free compost, coco coir, or fine bark). Species from winter-rainfall regions (many Crassula, Adromischus, Tylecodon, Dudleya) benefit from an even higher mineral fraction (80% or more). Container-grown plants should always be in pots with drainage holes — no gravel-only “drainage layers” at the bottom, which create a perched water table.

Watering

The golden rule across the family: less water is better. Water deeply when the substrate has dried completely, then allow it to dry out again before the next watering. In practice, this means watering every 7–14 days during the growing season and dramatically reducing or eliminating water during dormancy. Overwatering causes root rot, stem rot, and oedema far more reliably than underwatering causes death. Most Crassulaceae can tolerate weeks — even months — of drought without lasting damage, thanks to their CAM metabolism and water-storing tissues.

Crucially, respect the growth season of each genus. Winter-growers (Aeonium, Dudleya, Tylecodon, many Crassula) need water from autumn through spring and near-complete dryness in summer. Summer-growers (Echeveria, Graptopetalum, Pachyphytum, most Sedum) follow the reverse pattern. Ignoring dormancy rhythms is one of the most common causes of unexplained decline in collections.

Light

Most Crassulaceae are sun-loving plants that require at least 4–6 hours of direct sunlight daily for compact, well-coloured growth. Insufficient light causes etiolation — stretched stems, pale leaves, and weakened structure — which is the most frequent issue in indoor cultivation. South-facing windows (in the Northern Hemisphere) or supplementary LED grow lights are essential for indoor growers.

Notable exceptions exist: forest-origin Kalanchoe, some Adromischus, and creeping Crassula species prefer bright indirect light or dappled shade. Farinose species (Dudleya, farinose Echeveria) are sun-tolerant but should not have their wax coating disturbed by overhead watering or handling.

Temperature and hardiness

The family spans an enormous hardiness range. At one extreme, Sempervivum and Rhodiola species tolerate temperatures well below –30 °C (USDA zone 3 or even zone 1). At the other, tropical Kalanchoe species suffer damage below 5 °C. Most popular Crassulaceae for indoor and Mediterranean gardens — Crassula ovata, Echeveria, Graptopetalum, Aeonium — tolerate brief frosts to approximately –2 to –4 °C (USDA zone 9b–10a) when kept dry, but sustained freezing kills them. Winter protection (cold greenhouse, unheated room, frost fleece) is necessary in continental climates for these genera.

Fertilisation

Crassulaceae are modest feeders. A balanced liquid fertiliser at half the manufacturer’s recommended concentration, applied two to four times during the growing season, is sufficient. Avoid fertilising during dormancy. Excess nitrogen promotes soft, etiolated growth that is vulnerable to pests and rot.

Propagation

The Crassulaceae are among the easiest plant families to propagate, which partly explains their popularity. Common methods include leaf cuttings (particularly effective in Echeveria, Graptopetalum, Sedum, Pachyphytum, and many Crassula), stem cuttings (suitable for almost all genera), division of offsets (the natural propagation mode of Sempervivum, Jovibarba, and stoloniferous Sedum), and seed (the only viable method for species that do not offset, such as solitary Aeonium or non-branching Echeveria). The viviparous Kalanchoe species (former Bryophyllum) produce plantlets directly on leaf margins — a reproductive strategy so effective it makes several species invasive weeds in tropical regions.

Common Pests and Diseases

The Crassulaceae share a broadly similar pest and disease profile across genera. Here are the main threats to watch for:

Mealybugs

Mealybugs (Pseudococcidae) are the most common pest of indoor and greenhouse-grown Crassulaceae. They appear as white, cottony clusters in leaf axils, at the base of rosettes, and on roots. Root mealybugs are insidious because they remain invisible until the plant shows general decline. Treatment involves manual removal with isopropyl alcohol for light infestations, or systemic insecticide application for heavier attacks. Regular inspection is the best prevention — isolate any new plant for two to three weeks before introducing it to an existing collection.

Scale insects

Hard and soft scale occasionally attack Crassulaceae, particularly woody-stemmed genera like Crassula, Cotyledon, and Kalanchoe. They appear as immobile, waxy bumps on stems and leaf undersides. Horticultural oil or systemic insecticide are the usual controls.

Aphids

Aphids attack flower stalks and young growth in spring. They are particularly drawn to Aeonium, Sempervivum, and Echeveria inflorescences. Insecticidal soap or a strong water spray usually suffices.

Root rot (Pythium, Phytophthora, Fusarium)

By far the most lethal disease complex. Root rot results from a combination of overwatering, poorly draining substrate, and cool temperatures. Prevention is always preferable to cure: use mineral-heavy substrates, terracotta pots, and allow thorough drying between waterings. Once stem rot is visible (dark, translucent tissue at the base), the only recourse is to cut above the rotted area, allow the wound to callus, and re-root the cutting in dry substrate.

Powdery mildew

A common fungal issue in humid conditions with poor air circulation, particularly affecting Kalanchoe, Echeveria, and Crassula. White powdery patches appear on leaf surfaces. Improve ventilation, reduce humidity, and apply sulphur-based or potassium bicarbonate fungicides.

Etiolation

Not a disease per se, but the single most frequent cultural problem in Crassulaceae. Insufficient light causes stretched internodes, pale colour, and structurally weak growth. The solution is simple: more light — either by relocating outdoors seasonally or by supplementing with full-spectrum LED grow lights. Etiolated growth cannot be reversed on existing tissue; the remedy is to behead the rosette or cut the stem and re-root under better light conditions.

Crassulaceae in the Landscape and in Containers

Mediterranean and warm-temperate gardens (USDA 9–11)

In frost-free or mild-frost climates, Crassulaceae offer year-round structure and colour. Aeonium arboreum ‘Zwartkop’, Crassula ovata, Cotyledon orbiculata, and Senecio–Curio companions create low-water, low-maintenance plantings. Groundcover species such as Sedum sediforme, Sedum album, and Crassula multicava can replace conventional lawns on slopes.

Cold-climate gardens (USDA 3–8)

Sempervivum, Jovibarba, Sedum (hardy species), Hylotelephium, and Rhodiola thrive in rock gardens, wall crevices, alpine troughs, and green roofs. These genera tolerate extreme cold, poor soils, and full sun with minimal maintenance.

Indoor and container cultivation

The majority of the family performs well in containers, which allow precise control over substrate and watering. Key success factors indoors are maximising light (south-facing windows or grow lights), using unglazed clay pots for better aeration, and avoiding saucers that retain water. Grouping plants by growth season simplifies watering schedules — keep winter-growers and summer-growers on separate trays if possible.

Green roofs

Hardy Sedum and Sempervivum are the foundation of extensive green roof systems worldwide. Their shallow root systems, drought tolerance, and mat-forming growth make them ideal for lightweight, low-maintenance rooftop plantings. Sedum album, Sedum acre, Sedum sexangulare, Sedum rupestre, and Sedum spurium are among the most widely used species in the green roof industry.

Conservation

While many Crassulaceae are common and widespread, several genera contain critically endangered species threatened by habitat loss, illegal collection, and climate change. Dudleya species along the California and Baja California coasts have been the target of systematic poaching for the Asian succulent market, prompting new legal protections and active enforcement. Several South African Adromischus and Crassula species have extremely restricted ranges and face pressure from urban expansion and agriculture. Macaronesian endemics (Aeonium, Monanthes) are vulnerable to introduced herbivores and habitat fragmentation. Responsible growers should source plants from reputable nurseries propagating from cultivated stock, rather than supporting wild collection.

Frequently Asked Questions

What is the difference between Crassulaceae and “succulents” in general?

Crassulaceae is one botanical family; “succulent” is a horticultural term describing any plant with thickened, water-storing tissues. Many plant families contain succulents — Asphodelaceae (aloes, haworthias), Cactaceae (cacti), Asparagaceae (agaves), Euphorbiaceae (succulent euphorbias), Aizoaceae (living stones), and others. All Crassulaceae are succulents, but most succulents are not Crassulaceae.

Why is my Crassulaceae plant stretching and losing colour?

This is etiolation caused by insufficient light. Move the plant to a brighter location — ideally direct sunlight for at least four to six hours daily — or install a full-spectrum LED grow light. The stretched growth cannot revert, but new growth under adequate light will be compact and well-coloured.

Can I grow Crassulaceae outdoors in a cold climate?

Yes, but genus choice matters enormously. Sempervivum, Jovibarba, most Sedum, Hylotelephium, and Rhodiola are fully hardy to USDA zones 3–5 and thrive in rock gardens and green roofs. Frost-tender genera like Echeveria, Crassula, Kalanchoe, and Aeonium must be overwintered indoors or in a frost-free greenhouse in cold climates.

How often should I water my Crassulaceae plants?

There is no universal schedule. The guiding principle is: water deeply when the substrate is completely dry, then wait until it dries again. In practice, this may mean every 7–10 days in summer and once a month or less in winter for summer-growing species — and the reverse for winter-growers. When in doubt, wait an extra few days. Less water is better.

Are Crassulaceae toxic to pets?

Toxicity varies by genus. Kalanchoe species contain cardiac glycosides toxic to dogs, cats, and livestock. Tylecodon and Cotyledon species are notably toxic — Tylecodon wallichii is responsible for significant livestock losses in South Africa (the condition is called “krimpsiekte”). Crassula ovata is mildly toxic to cats and dogs. Sempervivum and most Sedum species are generally considered non-toxic. Always verify toxicity for any species accessible to pets or children.

What is the easiest Crassulaceae genus for beginners?

Crassula (especially Crassula ovata), Sedum, and Sempervivum are the most forgiving genera. They tolerate a wide range of conditions, propagate easily, and recover well from cultivation mistakes. Echeveria is also beginner-friendly but less tolerant of overwatering and low light.

Useful Websites on Crassulaceae

The following websites provide reliable information, photographs, and taxonomic databases relevant to the Crassulaceae. Inclusion does not imply endorsement; always cross-check nomenclature against POWO for accepted names.

Taxonomic databases and nomenclature

• Plants of the World Online (POWO) — https://powo.science.kew.org/ — Maintained by the Royal Botanic Gardens, Kew. The authoritative global reference for accepted plant names, synonymy, and distribution. Essential starting point for verifying any Crassulaceae species name.
• World Flora Online (WFO) — https://www.worldfloraonline.org/ — A collaborative effort aiming to compile a comprehensive online flora of all known plants. Includes morphological descriptions and nomenclatural data for Crassulaceae genera.
• International Plant Names Index (IPNI) — https://www.ipni.org/ — Nomenclatural database for vascular plant names. Useful for tracking publication details, author citations, and basionyms.
• GBIF (Global Biodiversity Information Facility) — https://www.gbif.org/ — Open-access occurrence and distribution data. Useful for mapping the natural range of Crassulaceae species based on herbarium and field records.

Specialist Crassulaceae websites

• International Crassulaceae Network (ICN) — https://www.crassulaceae.ch/ — A multilingual community platform with forums, photographic galleries, and reprints of scientific papers. Founded by Margrit Bischofberger. Free membership. Covers all genera, with particularly strong coverage of European and South African taxa.
• Crassulaceae.com — https://www.crassulaceae.com/ — A botanical database focused on American Crassulaceae, with extensive photographic documentation from natural localities. Maintained by a team of volunteer field botanists since 1997. Excellent for Echeveria, Sedum, Graptopetalum, Pachyphytum, Villadia, and Dudleya.
• The Encyclopaedia of Succulents — https://www.succulents.net/ — Comprehensive species-level encyclopedia covering Crassulaceae and other succulent families. Detailed care guides, morphological descriptions, and cultivation advice for hundreds of species. Trilingual (English, French, Italian).
• Succulent Plant Page — Crassulaceae — https://succulent-plant.com/families/crassulaceae.html — A well-established reference site with photographs and brief descriptions for many cultivated Crassulaceae species.

Broader succulent and botanical resources

• LLIFLE (Encyclopedia of Living Forms) — https://www.llifle.com/ — Community-driven encyclopedia covering cacti and succulents, including many Crassulaceae species. Extensive photographic galleries and basic cultivation data.
• iNaturalist — https://www.inaturalist.org/ — Citizen science platform with millions of georeferenced observations. Useful for seeing Crassulaceae in their natural habitats and for distribution mapping.
• JSTOR Global Plants — https://plants.jstor.org/ — Digital repository of herbarium specimens from institutions worldwide. Valuable for examining type specimens and historical collections of Crassulaceae.
• Cactus and Succulent Society of America (CSSA) — https://cactusandsucculentsociety.org/ — The largest succulent plant society in North America. Publishes the Cactus and Succulent Journal, which regularly features Crassulaceae research.
• British Cactus and Succulent Society (BCSS) — https://www.bcss.org.uk/ — Long-established UK society with a journal, forums, and plant shows. Strong coverage of Sempervivum, Aeonium, and South African Crassulaceae.

Bibliography

POWO (2026). Plants of the World Online. Royal Botanic Gardens, Kew. Available at: https://powo.science.kew.org/

Eggli, U. (ed.) (2003). Illustrated Handbook of Succulent Plants: Crassulaceae. Springer, Berlin.

‘t Hart, H. (1995). Infrafamilial and generic classification of the Crassulaceae. In: ‘t Hart, H. & Eggli, U. (eds.), Evolution and Systematics of the Crassulaceae, pp. 159–172. Backhuys, Leiden.

Messerschmid, T.F.E., Forrest, A., Chin, S.-W., Esk, A., Theodoridis, S. & Kadereit, J.W. (2020). Linnaeus’s folly – phylogeny, evolution and classification of Sedum (Crassulaceae) and Crassulaceae subfamily Sempervivoideae. Taxon, 69(5): 892–926.

Mort, M.E., Soltis, D.E., Soltis, P.S., Francisco-Ortega, J. & Santos-Guerra, A. (2001). Phylogenetic relationships and evolution of Crassulaceae inferred from matK sequence data. American Journal of Botany, 88(1): 76–91.

Mort, M.E., O’Leary, T.R., Carrillo-Reyes, P., Nowell, T., Archibald, J.K. & Randle, C.P. (2010). Phylogeny and evolution of Crassulaceae: past, present, and future. Schumannia, 6: 69–86.

Thiede, J. & Eggli, U. (2007). Crassulaceae. In: Kubitzki, K. (ed.), The Families and Genera of Vascular Plants, vol. 9, pp. 83–118. Springer, Berlin.

Toelken, H.R. (1985). Crassula. In: Leistner, O.A. (ed.), Flora of Southern Africa, vol. 14. Botanical Research Institute, Pretoria.

Van Ham, R.C.H.J. & ‘t Hart, H. (1998). Phylogenetic relationships in the Crassulaceae inferred from chloroplast DNA restriction-site variation. American Journal of Botany, 85(1): 123–134.