Haworthia

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Haworthia
Haworthia cymbiformis 1.jpg
Haworthia cymbiformis in cultivation
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Asphodelaceae
Subfamily: Asphodeloideae
Tribe: Aloeae
Genus: Haworthia
Duval
Synonyms [1]
  • ApicraWilld.
  • CatevalaMedik.
  • × ApworthiaPoelln.

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

Contents

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 of 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]

A selection of Haworthia plants in cultivation Haworthia (5630126865).jpg
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.

Related Research Articles

<i>Haworthia cymbiformis</i> Species of succulent

Haworthia cymbiformis is a species of the genus Haworthia in the family Asphodelaceae, endemic to the Eastern Cape Province in South Africa.

<i>Haworthia truncata</i> Species of succulent

Haworthia truncata, locally known as horse's teeth, is a species of succulent plant in the genus Haworthia. It is found in the Little Karoo region, in the far east of the Western Cape Province, South Africa.

<i>Haworthia magnifica</i> Species of succulent

Haworthia magnifica is a species of the genus Haworthia belonging to the family Asphodelaceae.

<i>Haworthia mirabilis</i> Species of succulent

Haworthia mirabilis is a species of the genus Haworthia belonging to the family Asphodelaceae.

<i>Tulista</i> Genus of flowering plants

Tulista is a small genus of succulent plants endemic to the Cape Provinces of South Africa. They were formerly included within the genus Haworthia.

<i>Haworthia cooperi</i> Species of succulent

Haworthia cooperi is a diverse and varied species of the genus Haworthia in the family Asphodelaceae, endemic to the Eastern Cape Province in South Africa.

<i>Haworthia retusa</i> Species of succulent

Haworthia retusa is a species of flowering plants of the genus Haworthia in the family Asphodelaceae, endemic to a very small area around Riversdale, in the Western Cape Province in South Africa. Growing to 10 cm (3.9 in) tall and broad, it is a perennial succulent with thick triangular leaves and small white tubular flowers held in 50 cm (20 in) tall racemes.

<i>Haworthia mucronata</i> Species of succulent

Haworthia mucronata is a species of the genus Haworthia in the family Asphodelaceae, endemic to the Little Karoo region, in the Western Cape Province of South Africa.

<i>Haworthia pygmaea</i> Species of succulent

Haworthia pygmaea is a species of the genus Haworthia in the family Asphodelaceae, endemic to the Mossel Bay area of the Western Cape, South Africa.

<i>Haworthia bayeri</i> Species of succulent

Haworthia bayeri is a species of the genus Haworthia in the family Asphodelaceae, endemic to the southern Cape Provinces in South Africa.

<i>Haworthiopsis scabra</i> Species of succulent

Haworthiopsis scabra, formerly Haworthia scabra, is a species of flowering succulent plant from arid regions of the Western and Eastern Cape Provinces, South Africa.

<i>Haworthia zantneriana</i> Species of succulent

Haworthia zantneriana is a species of the genus Haworthia in the family Asphodelaceae, subfamily Asphodeloideae, endemic to the southern parts of the Western Cape and Eastern Cape Provinces in South Africa.

<i>Haworthia arachnoidea</i> Species of succulent

Haworthia arachnoidea, locally known as "papierrosie" (paper-rose) or "spinnekopnes" (spider-nest), is the type species of the genus Haworthia, in the family Asphodelaceae, in the Western Cape Province of South Africa.

<i>Tulista pumila</i> Species of flowering plant

Tulista pumila ("Vratjiesaalwee") is a species of Tulista succulent plant, from the Western Cape, South Africa.

<i>Tulista kingiana</i> Species of succulent plant from the Western Cape, South Africa

Tulista kingiana is a species of succulent plant, from the Western Cape, South Africa. It is listed as Endangered on the IUCN global Red List.

<i>Haworthiopsis</i> Genus of succulent plants

Haworthiopsis is a genus of succulent plants in the subfamily Asphodeloideae. The genus was previously included in Haworthia. Species in the genus are typically short perennial plants, with leaves often arranged in a rosette and frequently having raised white markings. The two-lipped flowers are borne on a tall stalk and are small – less than 17 mm (0.7 in) long – and pale in colour. Many species are cultivated as house plants or by succulent enthusiasts.

<i>Haworthia turgida</i> Species of succulent

Haworthia turgida, also sometimes known as the windowpane plant, is a species of Haworthia native to the Cape Provinces. Its common name comes from the translucent panes on its leaves, which are similar to those of Haworthia cooperi and some other species in the genus. It grows in dense clusters of offsets from the base, and in its native habitat prefers rocky limestone or slate cliffs. The main type has pale green leaves but varies widely. Varieties include Haworthia turgida var. longibracteata (M.B.Bayer) and Haworthia turgida var. suberecta (Poelln.)

<i>Haworthia rossouwii</i> Species of succulent

Haworthia rossouwii is a species of succulent plant belonging to the genus Haworthia and is classified under the family Asphodelaceae. It is native to Southern Africa, in the Overberg region of the Western Cape Province.

<i>Haworthia reticulata</i> Species of plant

Haworthia reticulata is a species of succulent plant native to the southwestern Cape Provinces of South Africa. The species has several varieties, including var. hurlingii which is the smallest at up to 1 inch (2.5 cm) wide.

References

  1. 1 2 Kew World Checklist of Selected Plant Families
  2. Haworthia for the collector
  3. Stevens, P. F., Angiosperm Phylogeny Website: Asparagales: Asphodeloideae
  4. Bayer, B. (2012), Haworthia Update - Essays on Haworthia Vol. 7, Part 1.
  5. 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
  6. "All about Haworthia".
  7. The Plant List (2010). Version 1. Published on the Internet; http://www.theplantlist.org/ (accessed December 2012).
  8. "Search for Haworthia". World Checklist of Selected Plant Families . Royal Botanic Gardens, Kew . Retrieved 2018-02-21.
  9. 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.
  10. "Root Loss • Haworthia". www.haworthia.com. Archived from the original on 2018-01-18.
  11. The cultivation of different Haworthia species
  12. "Haworthia mucronata". hardiness.zone. Retrieved 15 August 2020.