Haworthia

Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Monocots
Ordo: Asparagales

Familia: Asphodelaceae
Subfamilia: Asphodeloideae
Genus: Haworthia
Overview of species

H. akaonii – H. angustifolia – H. ao-onii – H. arachnoidea – H. aristata – H. bayeri – H. blackburniae – H. bolusii – H. caesia – H. calva – H. chloracantha – H. compacta – H. cooperi – H. cymbiformis – H. decipiens – H. diaphana – H. elizeae – H. emelyae – H. floribunda – H. fukuyae – H. grenieri – H. heidelbergensis – H. herbacea – H. lockwoodii – H. maculata – H. magnifica – H. maraisii – H. marumiana – H. minor – H. mirabilis – H. mollis – H. monticola – H. mucronata – H. mutica – H. nortieri – H. outeniquensis – H. parksiana – H. pubescens – H. pulchella – H. pygmaea – H. regina – H. reticulata – H. retusa – H. rossouwii – H. sapphaia – H. semiviva – H. springbokvlakensis – H. subularis – H. transiens – H. truncata – H. turgida – H. variegata – H. veltina – H. villosa – H. vlokii – H. wittebergensis – H. zantneriana
Name

Haworthia Duval, Pl. Succ. Horto Alencon.: 7 (1809) nom. cons.

Type species: H. arachnoidea (L.) Duval

Synonyms

Homotypic
Apicra Willd., Mag. Neuesten Entdeck. Gesammten Naturk. Ges. Naturf. Freunde Berlin 5: 167. 1811, nom. illeg.
Heterotypic
Catevala Medik., Theodora: 67. (1786)
Type species: non design.
Kumaria Raf., Autik. Bot.: 137 (1840)
× Apworthia Poelln., J. Roy. Hort. Soc. 68: 259. (1943)
Type species: non design.

Distribution
Native distribution areas:

Africa
Southern Africa
Cape Provinces, Free State.

References: Brummitt, R.K. 2001. TDWG – World Geographical Scheme for Recording Plant Distributions, 2nd Edition
References
Primary references

Duval, H.A. 1809. Plantae succulentae, in Horto Alenconio 7.

Links

Govaerts, R. et al. 2019. Haworthia in Kew Science Plants of the World online. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the internet. Accessed: 2019 March 3. Reference page.
Govaerts, R. et al. 2019. Haworthia in World Checklist of Selected Plant Families. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the internet. Accessed: 2019 March 3. Reference page.
International Plant Names Index. 2019. Haworthia. Published online. Accessed: 3 March 2019.
The Plant List 2013. Haworthia in The Plant List Version 1.1. Published on the internet. Accessed: 2019 March 3.
Tropicos.org 2019. Haworthia. Missouri Botanical Garden. Published on the internet. Accessed: 2019 March 3.

Vernacular names

čeština: Havortie
فارسی: هاوورتیا
suomi: Kirjotähdet
hrvatski: Havorcija
日本語: ハオルシア属
polski: Haworsja
русский: Хавортия
svenska: Haworthiasläktet
українська: Гавортія
中文: 十二卷属

Haworthia is a large genus of small succulent plants endemic to Southern Africa (Mozambique, Namibia, Lesotho, Eswatini and South Africa).[1]

Like the aloes, they are members of the subfamily Asphodeloideae and they generally resemble miniature aloes, except in their flowers, which are distinctive in appearance. They are popular garden and container plants.

Description and characteristics

Haworthias are small succulent plants, forming rosettes of leaves from 3 cm (1.2 in) to exceptionally 30 cm (12 in) in diameter, depending on the species. These rosettes are usually stemless but in some species stems reach up to 50 cm (20 in). The inflorescences of some species may exceed 40 cm (16 in) in height. The plants can grow solitary or can be clump-forming. Many species have firm, tough, fleshy leaves, usually dark green in colour, whereas others are softer and contain leaf windows with translucent panels through which sunlight can reach internal photosynthetic tissues. Their flowers are small, and generally white. Though they are very similar between species, flowers from the species in section Hexangulares generally have green striations and those from other species often have brown lines in the flowers. However, their leaves show wide variations even within one species. Additionally, when the plants are stressed (e.g. deprived of water), their colours can change to reds and purples. Depriving them of nitrogen generally results in paler leaves.[2]
Distribution

Most species are endemic to South Africa, with the greatest species diversity occurring in the south-western Cape. Some species do however extend into neighbouring territories, in Eswatini (formerly Swaziland), southern Namibia and southern Mozambique (Maputaland).
Naming and taxonomy

Haworthia is a genus within the family Asphodelaceae, subfamily Asphodeloideae. The genus is named after the botanist Adrian Hardy Haworth. B. Bayer recognised approximately 60 species in a review of the genus in 2012, whereas other taxonomists are very much less conservative. Related genera are Aloe, Gasteria and Astroloba and intergeneric hybrids are known. [3][4]
Subdivisions

The classification of the flowering plant subfamily Asphodeloideae is weak, and concepts of the genera are not well substantiated. Haworthia has been a similarly a weakly contrived genus. Because of their horticultural interest, its taxonomy has been dominated by amateur collectors, and the literature is rife with misunderstanding of what the taxa actually are or should be. Recent phylogenetic studies have demonstrated that the traditional divisions of the genus are actually relatively unrelated (Hexangulares was shown to be a sister-group of genus Gasteria, Robustipedunculares more closely related to genus Astroloba, and Haworthia as an out-group related to Aloe). In recognition of the polyphyletic nature of the genus, Haworthiopsis and Tulista have been split off.

Botanists had long noticed differences in the flowers the three subgenera, but had previously considered those differences to be inconsequential, although the differences between species in the same subgenus definitely are. The roots, leaves and rosettes do demonstrate some generic differences while wide variations occur even within one species.[5][6]
Species

Many species of Haworthia have been moved to Haworthiopsis and Tulista, in particular since the last update of The Plant List (2013), which contains about 150 accepted species of Haworthia. The actual number and identification of the species is not well established; many species are listed as "unresolved" for lack of sufficient information, and the full list reflects the difficulties of Haworthia taxonomy, including many varieties and synonyms.[7] The World Checklist of Selected Plant Families has been updated to exclude the species now in Haworthiopsis and Tulista. The species it accepts as of February 2018 are listed below,[8] excluding Haworthia kingiana and Haworthia minor, placed in Tulista by other sources.[9]

Haworthia akaonii M.Hayashi – Western Cape Provinces
Haworthia angustifolia Haw. – Southern Cape Provinces
Haworthia ao-onii M.Hayashi – Cape Provinces
Haworthia arachnoidea (L.) Duval – Southwestern Cape Provinces
Haworthia aristata Haw. – Southern Cape Provinces
Haworthia bayeri J.D.Venter & S.A.Hammer – Southwestern Cape Provinces
Haworthia blackburniae W.F.Barker – Southwestern Cape Provinces
Haworthia bolusii Baker – Southern central and southern Cape Provinces to Free State
Haworthia caesia M.Hayashi – Western Cape Provinces
Haworthia calva M.Hayashi – Eastern Cape Provinces
Haworthia chloracantha Haw. – Southwestern Cape Provinces
Haworthia compacta (Triebner) Breuer – Cape Provinces
Haworthia cooperi Baker – Southern Cape Provinces
Haworthia cymbiformis (Haw.) Duval – Southern and southeastern Cape Provinces
Haworthia decipiens Poelln. – Southern Cape Provinces
Haworthia diaphana M.Hayashi – Eastern Cape Provinces
Haworthia elizeae Breuer – Western Cape Provinces
Haworthia emelyae Poelln. – Southwestern Cape Provinces
Haworthia floribunda Poelln. – Southwestern Cape Provinces
Haworthia fukuyae M.Hayashi – Eastern Cape Provinces
Haworthia grenieri Breuer – Western Cape Provinces
Haworthia heidelbergensis G.G.Sm. – Southwestern Cape Provinces
Haworthia herbacea (Mill.) Stearn – Southwestern Cape Provinces
Haworthia lockwoodii Archibald – Southwestern Cape Provinces
Haworthia maculata (Poelln.) M.B.Bayer – Southwestern Cape Provinces
Haworthia magnifica Poelln. – Southwestern Cape Provinces
Haworthia maraisii Poelln. – Southwestern Cape Provinces
Haworthia marumiana Uitewaal – Cape Provinces
Haworthia mirabilis (Haw.) Haw. – Southwestern Cape Provinces
Haworthia mollis M.Hayashi – Eastern Cape Provinces
Haworthia monticola Fourc. – Southwestern Cape Provinces
Haworthia mucronata Haw. – Southwestern Cape Provinces
Haworthia mutica Haw. – Southwestern Cape Provinces
Haworthia nortieri G.G.Sm. – Southwestern Cape Provinces
Haworthia outeniquensis M.B.Bayer – Southwestern Cape Provinces
Haworthia parksiana Poelln. – Southwestern Cape Provinces
Haworthia pubescens M.B.Bayer – Southwestern Cape Provinces
Haworthia pulchella M.B.Bayer – Southwestern Cape Provinces
Haworthia pygmaea Poelln. – Southwestern Cape Provinces
Haworthia regina M.Hayashi – Eastern Cape Provinces
Haworthia reticulata (Haw.) Haw. – Southwestern Cape Provinces
Haworthia retusa (L.) Duval – Southwestern Cape Provinces
Haworthia rossouwii Poelln. – Cape Provinces
Haworthia sapphaia M.Hayashi – Eastern Cape Provinces
Haworthia semiviva (Poelln.) M.B.Bayer – Cape Provinces
Haworthia springbokvlakensis C.L.Scott – Southern Cape Provinces
Haworthia subularis M.Hayashi – Eastern Cape Provinces
Haworthia transiens (Poelln.) M.Hayashi – Southern Cape Provinces
Haworthia truncata Schönland – Southwestern Cape Provinces
Haworthia turgida Haw. – Southwestern Cape Provinces
Haworthia variegata L.Bolus – Southwestern Cape Provinces
Haworthia veltina M.Hayashi – Eastern Cape Provinces
Haworthia villosa M.Hayashi – Eastern Cape Provinces
Haworthia vlokii M.B.Bayer – Southwestern Cape Provinces
Haworthia wittebergensis W.F.Barker – Southwestern Cape Provinces
Haworthia zantneriana Poelln. – Southern Cape Provinces

A selection of Haworthia plants in cultivation
Cultivation

There is widespread special collector interest, and some species such as Haworthia cymbiformis are fairly common house and garden plants.

Almost all Haworthia species are naturally adapted for semi-shade conditions (in habitat they tend to grow under bushes or rock overhangs) and they are therefore healthiest in shade or semi-shade. Some species like Haworthia pumila and Haworthia truncata can be adapted to tolerate full-sun however.

All Haworthia species favour extremely well-drained soil (in habitat they tend to grow in poor sands, in rocky areas). Watering depends on the species (winter or summer rainfall) but most of the common species are tolerant of a variety of watering routines. Over-watering can cause the roots to rot.[10] Rarer species may have more specific requirements.[11] All haworthias are sensitive to frost, and they are rated as winter hardy to USDA zone 10.[12]

Haworthia species reproduce both through seed and through budding, or offsets. Certain species or clones may be more successful or rapid in offset production, and these pups are easily removed to yield new plants once a substantial root system has developed on the offshoot. Less reliably, the plants may also be propagated through leaf cuttings, and in some instances, through tissue culture.
Gallery for identification

Haworthia arachnoidea has numerous dark-green leaves, which have no translucent tips and bear a dense hairy web of spines.

Haworthia nortieri, from the far north-west of the Western Cape, has opaque leaves, covered in oval, pellucid spots.

Haworthia maculata, showing distinctive red-purple, spotted, normally turgid leaves, with tiny bristles on margins & keels.

The highly proliferous Haworthia reticulata bears tiny teeth and a reticulated pattern on its leaves.

Haworthia herbacea, showing distinctive yellow-green ("herbacea") colour, and spined margins & keels.

Haworthia pubescens co-occurs with H.herbacea but is very finely "pubescent" (covered in velvety fur)

Haworthia floribunda has relatively few dark, slender, twisted leaves with rounded ends.

Haworthia chloracantha forms clumps with slender, curved, yellow-green leaves

Haworthia variegata has thin, straight, erect leaves, with variegated spined margins.

Haworthia maraisii is a tiny, dark-coloured haworthia, with bristled, retused leaves.

Haworthia parksiana, the smallest Haworthia species.

Haworthia mirabilis has sharp-pointed, translucent leaf faces with marginal spines

Haworthia mirabilis var. badia has reddish-brown, attenuate leaves

Haworthia heidelbergensis possibly a form of H. mirabilis, with long, thin, bristle-tipped leaves, that are more outward spreading.

Haworthia magnifica is sometimes considered to be a form of H. mirabilis. It is distinguished by its flowers, but usually has dark, lined, triangular, scabrid leaf-faces.

Haworthia magnifica var. splendens is a particularly ornate variety with flecked leaves, prized by horticulturalists as "Haworthia splendens".

Haworthia magnifica var. acuminata has a lighter colour and more pointed, "acuminate" leaves

Haworthia magnifica var. atrofusca is a very dark, reddish-brown, rough-surfaced variety

Haworthia turgida is a compact, clumping, retuse haworthia, with swollen, "turgid", light-green leaves

Haworthia mutica has one or two lines and a pale, cloudy, mat surface on its compact, slightly rounded ("mutica") leaves

Haworthia retusa has a recognisable shiny leaf-face on its retuse leaves, and a light green colour

Haworthia pygmaea has flat, rough, scabrous or papillate leaf surfaces

"agenteo-maculosa" is a smoother variety of Haworthia pygmaea with silver spots ("argenteo maculosa")

Haworthia emelyae has compact, bulging leaves which are often pink-flecked.

Haworthia bayeri has dark leaves with slightly rounded leaf tips.

Haworthia emelyae var. comptoniana is a large, lighter coloured form, with a clear reticulated pattern on the broad leaf faces

Haworthia springbokvlakensis has round, bulging, translucent leaf faces

Haworthia truncata ("Horse's teeth")

Haworthia wittebergensis showing its distinctive thin bristle-like leaves

Haworthia semiviva drys its leaves into a papery sheath in the heat of summer.

Haworthia lockwoodii drys its leaves into a papery sheath in the heat of summer.

Haworthia marumiana var. redii

Haworthia mucronata has translucent margins and keels on its soft, pointed ("mucronate") leaves.

Haworthia decipiens has light green, wide, flat, semi-translucent leaves, that have prodigious bristles on the margins (less so on the bottom leaf faces)

Haworthia cooperi (showing translucent "window" panels at the tips of its leaves)

An extreme rounded form of Haworthia cooperi

Haworthia cymbiformis has light green, even-coloured, boat-shaped leaves ("cymbiformis" = "boat shaped")

Haworthia blackburneae is a thin, grass-like species

References

Kew World Checklist of Selected Plant Families
Haworthia for the collector
Stevens, P.F., Angiosperm Phylogeny Website: Asparagales: Asphodeloideae
Bayer, B. (2012), Haworthia Update - Essays on Haworthia Vol. 7, Part 1.
Manning, John; Boatwright, James S.; Daru, Barnabas H.; Maurin, Olivier; van der Bank, Michelle. A Molecular Phylogeny and Generic Classification of Asphodelaceae subfamily Alooideae: A Final Resolution of the Prickly Issue of Polyphyly in the Alooids? Systematic Botany, Volume 39, Number 1, March 2014, pp. 55-74
"All about Haworthia".
The Plant List (2010). Version 1. Published on the Internet; http://www.theplantlist.org/ (accessed December 2012).
"Search for Haworthia". World Checklist of Selected Plant Families. Royal Botanic Gardens, Kew. Retrieved 2018-02-21.
Manning, John; Boatwright, James S.; Daru, Barnabas H.; Maurin, Olivier & Bank, Michelle van der (2014). "A Molecular Phylogeny and Generic Classification of Asphodelaceae Subfamily Alooideae: A Final Resolution of the Prickly Issue of Polyphyly in the Alooids?". Systematic Botany. 39 (1): 55–74. doi:10.1600/036364414X678044. S2CID 86714657.
[1]
The cultivation of different Haworthia species
"Haworthia mucronata". hardiness.zone. Retrieved 15 August 2020.