Gasteria

Gasteria is a genus of succulent plants, native to South Africa (and the far south-west corner of Namibia).[1]

Gasteria
Gasteria pillansii
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Asphodelaceae
Subfamily: Asphodeloideae
Tribe: Aloeae
Genus: Gasteria
Duval
Synonyms[1]

Ptyas Salisb.

Naming

The genus is named for its stomach-shaped flowers ("gaster" is Latin for "stomach"). Common names include ox-tongue, cow-tongue, lawyer's tongue and, occasionally, mother-in-law's tongue.[2]

Description
Single flower of a Gasteria
Gasteria brachyphylla

Gasterias are recognisable from their thick, hard, succulent "tongue-shaped" leaves. Their inflorescence is also unique, with their curved, stomach-shaped flowers, which hang from inclined racemes.

Distribution
Gasteria rawlinsonii 'Staircase' (a cultivar) showing the distinctive pendulous, "stomach-shaped" Gasteria flowers

The species of this genus are mostly native to the Eastern Cape Province, South Africa, where the bulk of the species occurs – especially in the small area between Grahamstown and Uniondale which enjoys rainfall throughout the year. However distribution of several species extends widely across the low-altitude coastal regions of the country, in an arched horseshoe shape across South Africa. At the one end of the genus's distribution, a species Gasteria pillansii extends into the far south-west corner of Namibia. At the other end, a species reaches the Lebombo mountains of Swaziland.

Taxonomy
Distribution map of the various Gasteria species and subspecies in southern Africa

Gasteria is part of the family Asphodelaceae, subfamily Asphodeloideae. Closely related genera include Aloe and Haworthia, and the species of these genera are known to hybridise relatively easily with each other.[3]

Dividing Gasteria into species is extremely difficult, as each plant can be highly variable. One plant will look different depending on its location, its soil and its age. Young Gasteria plants typically look entirely different to older specimens. (Usually, young plants have flat, strap-shaped, highly tubercled leaves, in a distichous formation.) In addition, the species tend to flow into each other in gradual transitions, with many intermediate forms, rather than being cleanly divided into discrete and separate species. Lastly, hybrids occur easily and naturally, whenever the range of two species overlap in habitat.

There is therefore considerable disagreement on how many species exist, with as many as 100 names being listed. Current studies tend to agree that there are between 16 and 23 species.

Taxonomy according to flower morphology

Using morphology (especially flower structure), a traditional and widely accepted taxonomy was described in 1994 (van Jaarsveld et al.), dividing the genus into 2 sections, 4 series, and 21 species.

  • Section Longiflorae (2 series, 13 species)
    • Series Longifoliae (6 species):
      • Gasteria batesiana G.D.Rowley – Limpopo, Mpumalanga, KwaZulu-Natal
        • G. batesiana var. batesiana
        • G. batesiana var. dolomitica – Mpumalanga
      • Gasteria barbae van Jaarsv. – southern coast of Cape Province, between Knysna and Plettenberg Bay
      • Gasteria tukhelensis van Jaarsv. – KwaZulu-Natal
      • Gasteria croucheri (Hook.f.) Baker – south-east Cape Province to east KwaZulu-Natal
        • G. croucheri subsp. croucheri – south-east Cape Province to East KwaZulu-Natal
        • G. croucheri subsp. pendulifolia (van Jaarsv.) Zonn. – KwaZulu-Natal
        • G. croucheri subsp. pondoensis N.R.Crouch – south-east Cape Province
      • Gasteria acinacifolia (J.Jacq.) Haw. – southern coast of Cape Province
      • Gasteria polita van Jaarsv. – Cape Province
    • Series Multifariae (7 species):
      • Gasteria excelsa Baker – Transkei, Eastern Cape
      • Gasteria pulchra (Aiton) Haw. – Cape Province
      • Gasteria carinata (Mill.) Duval – south-south-west Cape Province
        • G. carinata var. carinata – Langeberg in Cape Province
        • G. carinata var. retusa van Jaarsv. – Worcester & Heidelberg in Cape Province
        • G. carinata var. thunbergii van Jaarsv.=G. thunbergii N.E.Br.[4] – near Herbertsdale in Cape Province
        • G. carinata var. verrucosa van Jaarsv. – Bredasdorp in Cape Province
      • Gasteria nitida (Salm-Dyck) Haw. – southern Cape Province
        • G. nitida var. nitida – southern Cape Province
        • G. nitida var. armstrongii (Schönland) van Jaarsv. / G. armstrongii Schönland – southern Cape Province
      • Gasteria ellaphieae van Jaarsv. – Kouga Dam in Cape Province
      • Gasteria glauca van Jaarsv – Cape Province
      • Gasteria vlokii van Jaarsv. – Great Swartberg + Witteberg in Cape Province (a higher altitude species)
  • Section Gasteria (2 series, 8 species)
    • Series Gasteria (7 species):
      • Gasteria obliqua (Aiton) Duval – south-east Cape Province; naturalized in Mexico
        • =G. bicolor (Aiton) Duval
        • =G. bicolor var. fallax (Haw.) van Jaarsv.
        • =G. bicolor var. liliputana (Poelln.) van Jaarsv.[5]
      • Gasteria disticha (L.) Haw. – Robertson Karoo and surrounds, Western Cape
        • G. disticha var. disticha – south-west and south-central Cape Province
        • G. disticha var. langebergensis van Jaarsv. – western Cape Province
        • G. disticha var. robusta van Jaarsv. – western Cape Province
      • Gasteria brachyphylla (Salm-Dyck) van Jaarsv. – Little Karoo in Cape Province
        • G. brachyphylla var. bayeri van Jaarsv. – Little Karoo in Cape Province
        • G. brachyphylla var. brachyphylla
      • Gasteria rawlinsonii Oberm. – Baviaanskloof in Cape Province
      • Gasteria glomerata van Jaarsv. – Kouga Dam in Cape Province
      • Gasteria baylissiana Rauh – Suurberg Range in Cape Province
      • Gasteria doreeniae van Jaarsv. & A.E.van Wyk – Cape Province
    • Series Namaquana (1 species):
      • Gasteria pillansii Kensit – Namibia, Cape Province
        • G. pillansii var. var. ernesti-ruschii (Dinter & Poelln.) van Jaarsv. – south-west Namibia to north-west Cape Province (Richtersveld)
        • G. pillansii var. hallii van Jaarsv. – western Cape Province
        • G. pillansii var. pillansii – western Cape Province

[6]

Taxonomy according to genome

A phylogenetic study in 2005[7] suggest that the genus may be sub-divided into 5 groups with respect to a increasing pattern in DNA content and geographical distribution:

Western distichous group

Species with distichous (two-ranked), strap-shaped leaves which are usually without keels.

Rare inland species
  • Gasteria glauca has rough-surfaced, blue-green leaves.
  • Gasteria ellaphieae forms rosettes of pointed, triangular, recurved, densely tuberculate leaves, and branched inflorescence.
  • Gasteria glomerata has distichous compact, round, glaucous, recurved rough-surfaced leaves, and forms dense clumps.
  • Gasteria vlokii forms rosettes of mat-surface, slightly rough, triangular (usually recurved), strap shaped leaves.
  • Adult Gasteria nitidas form rosettes of smooth, shiny, triangular leaves, with smooth (non-serrated) edges and true (non-marginiform) keels. Juvenile plants have recurved distichous, tubercled leaves.
  • Gasteria armstrongii is a very divergent form of Gasteria nitida which maintains into adulthood the dark, recurved, retuse, distichous, roughly tuberculate leaves.
  • Gasteria polita forms rosettes of short, triangular, smooth leaves, with rounded ends and strong keels
  • Gasteria doreeniae
  • Gasteria pulchra forms rosettes of smooth, thin, sharp, elongated, ascending leaves (linear triangular).

Large coastal group

Species generally form rosettes, with leaves usually bearing marginiform keels.

  • Gasteria carinata var carinata – the typical form. It has erect & spreading, rough, sparsely bumpy/tuberculate leaves
  • Gasteria carinata var carinata – the adult form with juvenile
  • Gasteria carinata var verrucosa is a proliferous variety with erect & spreading leaves that remain distichous and heavily tubercled into adulthood
  • Gasteria acinacifolia has slender, erect & spreading leaves with finely serrated edges. Heavily spotted.
  • Gasteria excelsa has smooth spreading leaves with a darker colour and sharply serrated edges.
  • Gasteria croucheri has smooth spreading, dark green, slightly glaucous leaves
  • Gasteria tukhelensis has slender, smooth and shiny leaves
  • Gasteria batesiana has leaves which are heavily tuberculate (bumpy/warty) and finely rululous (wrinkled).

Cultivation

Gasteria species are grown in well-drained, sandy soils in light shade. The species can all be propagated by off-sets and cuttings (leaf cuttings can usually be rooted easily). They are also commonly propagated by seed. Germination usually occurs within 8 days but may take as long as one month depending on the species.

Flowering times vary between species, but is usually in the spring & summer. Those in the summer rainfall areas to the east, tend to always flower in spring to summer (October–January in South Africa) such as Gasteria batesiana, Gasteria croucheri & Gasteria acinacifolia. Those in the areas which receive rainfall all year, usually flower also in later summer (December–January) such as Gasteria excelsa, Gasteria nitida, Gasteria vlokii and Gasteria brachyphylla var. bayeri. Others in this region flower all year, but with a peak in the spring, such as Gasteria rawlinsonii, Gasteria bicolor & Gasteria carinata. The western-most species vary in their flowering times, within the species. Gasteria pillansii in the far west, flowers in summer (December–January), except for its northern-most variety "var. ernesti-ruschii" which flowers in autumn (March–April). Gasteria disticha usually flowers in spring, but in the far north of its range near Beaufort West it flowers in December.[8]

Gasteria species are prone to Fusarium root rot, if they are over-watered. [9][10]

Several hybrids with species in other related genera have been created in cultivation, such as between Gasteria and Aloe (×Gasteraloe), and between Gasteria and Haworthia (×Gasterhaworthia).

References
  1. Kew World Checklist of Selected Plant Families
  2. Bailey, L.H.; Bailey, E.Z.; the staff of the Liberty Hyde Bailey Hortorium. 1976. Hortus third: A concise dictionary of plants cultivated in the United States and Canada. Macmillan, New York.
  3. Stevens, P.F., Angiosperm Phylogeny Website: Asparagales: Asphodeloideae
  4. Govaerts, R. "Gasteria carinata var. thunbergii - Synonyms". World Checklist of Selected Plant Families. the Royal Botanic Gardens, Kew. Retrieved 18 February 2018.
  5. Govaerts, R. (2014). "Gasteria obliqua - Synonyms". World Checklist of Selected Plant Families. the Royal Botanic Gardens, Kew. Retrieved 18 February 2018.
  6. "Search term=Gasteria". World Checklist of Selected Plant Families. the Royal Botanic Gardens, Kew. Retrieved 18 February 2018.
  7. B. J. M. Zonneveld, E. J. van Jaarsveld: Taxonomic implications of genome size for all species of the genus Gasteria Duval (Aloaceae). 24 Feb 2005
  8. E.J. van Jaarsveld: Gasterias of South Africa, A new revision of a major succulent group. Fernwood Press, Cape Town. p.19. ISBN 1-874950-01-6
  9. Propagation of Gasterias
  10. Gasteria
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