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.

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 16 species. E. J. van Jaarsveld has revised the taxonomy since then and the most recent synoptic review was published in 2007.[4] Several new species have been described in recent years, as well. Currently the number of accepted species is 29.

  • Section Longiflorae (2 series, 19 species)
    • Series Longifoliae (6 species):
      • Gasteria acinacifolia (J.Jacq.) Haw. – southern coast of Cape Province
      • Gasteria barbae van Jaarsv. – southern coast of Cape Province, between Knysna and Plettenberg Bay[5]
      • Gasteria batesiana G.D.Rowley – Limpopo, Mpumalanga, KwaZulu-Natal
        • G. batesiana var. batesiana G.D.Rowley
        • G. batesiana var. dolomitica van Jaarsv. & A.E.van Wyk – Mpumalanga
      • Gasteria croucheri Baker – south-east Cape Province to east KwaZulu-Natal
        • G. croucheri subsp. croucheri Baker – south-east Cape Province to East KwaZulu-Natal
        • G. croucheri subsp. pendulifolia (van Jaarsv.) Zonn. – KwaZulu-Natal
        • G. croucheri subsp. pondoensis N.R.Crouch, Gideon F.Sm. & D.Styles – south-east Cape Province[6]
      • Gasteria loedolffiae van Jaarsv. – Eastern Cape[7]
      • Gasteria tukhelensis van Jaarsv. – KwaZulu-Natal
  • Section Gasteria (2 series, 10 species)
    • Series Gasteria (9 species):
      • Gasteria baylissiana Rauh – Suurberg Range in Cape Province
      • Gasteria bicolor Haw. – south-east Cape Province; naturalized in Mexico
        • G. bicolor var. bicolor Haw.
        • G. bicolor var. fallax (Haw.) van Jaarsv.
        • G. bicolor var. liliputana (Poelln.) van Jaarsv.
      • Gasteria brachyphylla (Salm-Dyck) van Jaarsv. – Little Karoo in Cape Province
        • G. brachyphylla var. brachyphylla (Salm-Dyck) van Jaarsv.
        • G. brachyphylla var. bayeri van Jaarsv. – Little Karoo in Cape Province
      • Gasteria camillae van Jaarsv. & Molteno – Baviaanskloof mountain range[11]
      • Gasteria disticha (L.) Haw. – Robertson Karoo and surrounds, Western Cape
        • G. disticha var. disticha (L.) Haw. – south-west and south-central Cape Province
        • G. disticha var. robusta van Jaarsv. – western Cape Province
      • Gasteria doreeniae van Jaarsv. & A.E.van Wyk – Cape Province
      • Gasteria glomerata van Jaarsv. – Kouga Dam in Cape Province
      • Gasteria rawlinsonii Oberm. – Baviaanskloof in Cape Province
      • Gasteria retusa (van Jaarsv.) van Jaarsv. – Worcester & Heidelberg in Cape Province
    • Series Namaquana (1 species):
      • Gasteria pillansii Kensit – Namibia, Cape Province
        • G. pillansii var. pillansii Kensit – western Cape Province
        • G. pillansii var. ernesti-ruschii (Dinter von Poellnitz) van Jaarsv. – south-west Namibia to north-west Cape Province (Richtersveld)
        • G. pillansii var. hallii van Jaarsv. – western Cape Province

Taxonomy according to genome

A phylogenetic study in 2005[12] suggest that the genus may be sub-divided into 5 groups with respect to an 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 westernmost species vary in their flowering times, within the species. Gasteria pillansii in the far west, flowers in summer (December–January), except for its northernmost 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.[13]

Gasteria species are prone to Fusarium root rot, if they are over-watered. [14][15]

The cultivar 'Little Warty' [16] is a recipient of the Royal Horticultural Society's Award of Garden Merit.

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. van Jaarsveld, E. J. (2007). The genus Gasteria: a synoptic review (new taxa and combinations), Aloe, 44 (4), pp. 81-104.
  5. van Jaarsveld, E. J. (2014). Gasteria barbae, a new cliff-dwelling species from the Western Cape, South Africa, CactusWorld, 32 (4), pp. 257-260.
  6. Crouch, N.R., Smith, G.F. and Styles, D.G.A. (2011). Gasteria croucheri subsp. pondoensis, a new cremophyte from Pondoland, South Africa, Bothalia, 41, pp. 183-185.
  7. van Jaarsveld, E. J. (2014). Gasteria loedolffiae (Asphodelaceae). A new cliff-dwelling species from the Eastern Cape, South Africa, Bradleya, 32, pp. 44-49.
  8. van Jaarsveld, E. J. (2017). Gasteria koenii, a New Gasteria Species from the Swartberg, Western-Cape, South Africa. Haseltonia, 23, pp. 48-52.
  9. van Jaarsveld, E.J., Zonneveld, B.J.M., and Tribble, D.V. (2019). Gasteria langebergensis, a new status for a Gasteria from the Western Cape, South Africa. Bradleya, 37, pp. 167-171.
  10. van Jaarsveld, E. J. (2020). Gasteria visserii van Jaarsv., a new species from the Eastern Cape, South Africa. Bradleya, 38, pp. 26-29.
  11. van Jaarsveld, E. J. and Molteno, S. (2020). Gasteria camillae van Jaarsv. & Molteno, a new obligatory cliff-dwelling species from the Eastern Cape, South Africa. Bradleya, 38, pp. 20-25.
  12. 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
  13. 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
  14. Propagation of Gasterias
  15. Gasteria
  16. "Gasteria 'Little Warty'". RHS. Retrieved 8 July 2020.
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