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Allocasuarina humilis
	Immature and mature female cones
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Fagales
Family:	Casuarinaceae
Genus:	Allocasuarina
Species:	A. humilis
Binomial name
	Allocasuarina humilis; (Otto & A.Dietr.) L.A.S.Johnson
	Occurrence records downloaded from AVH, 22 June 2018
Synonyms
	List Casuarina humilis Otto & A.Dietr.; Casuarina humilis Otto & A.Dietr. var. humilis; Casuarina humilis var. macrocarpa Miq.; Casuarina preissiana Miq.; Casuarina selaginoides Miq.; Casuarina tephrosperma Miq.; ;

Allocasuarina humilis, commonly known as dwarf sheoak,^[2] is a species of flowering plant in the family Casuarinaceae and is endemic to the south-west of Western Australia. It is an erect or spreading dioecious or monoecious shrub that has its leaves reduced to scales in whorls of five to seven, the mature fruiting cones 12–22 mm (0.47–0.87 in) long containing winged seeds (samaras) 5–6 mm (0.20–0.24 in) long.

Description

Allocasuarina humilis is an erect or spreading, dioecious or monoecious shrub that typically grows to a height of 0.2–2 m (7.9 in – 6 ft 6.7 in). Its needle-like branchlets are more or less erect, up to 120 mm (4.7 in) long, the leaves reduced to scale-like teeth 0.4–0.5 mm (0.016–0.020 in) long, arranged in whorls of five to seven around the branchlets. The branchlets are smooth and sometimes waxy. The sections of branchlet between the leaf whorls (the "articles") are mostly 3–6 mm (0.12–0.24 in) long and 0.8–1.2 mm (0.031–0.047 in) wide. Male flowers are arranged in spikes 6–18 mm (0.24–0.71 in) long, in whorls of 12 to 16 per centimetre (per 0.39 in.), the anthers 0.7–0.8 mm (0.028–0.031 in) long. Flowering occurs from May to November, and the mature cones are sessile, 12–22 mm (0.47–0.87 in) long and 10–17 mm (0.39–0.67 in) in diameter containing samaras 5–6 mm (0.20–0.24 in) long with a short wing.^[2]^[3]^[4]

Taxonomy

This sheoak was first formally described in 1841 by Christoph Friedrich Otto and Albert Gottfried Dietrich, who gave it the name Casuarina humilis in their book Allgemeine Gartenzeitung.^[5]^[6] In 1982, Lawrie Johnson transferred it to the new genus Allocasuarina as A. humilis in the Journal of the Adelaide Botanic Gardens.^[7]^[8] The specific epithet (humilis) means "low, or low-growing".^[9]

A 2003 molecular study of the family Casuarinaceae showed dwarf sheoak and horned sheoak (A. thuyoides) to be sister taxa, and form a clade with A. thuyoides, A. microstachya, karri oak (A. decussata) and western sheoak (A. fraseriana),^[10] all from Western Australia.

Distribution and habitat

Allocasuarina humilis is found across southwest Western Australia, from the Murchison River in the north, to the south coast, where it extends eastwards to Israelite Bay. It grows on sand, sand over laterite, gravel, or clay.^[2]^[3]

Use in horticulture

Allocasuarina humilis adapts readily to cultivation. Versatile, it tolerates a wide range of soils, including those with some alkalinity, and prefers a sunny aspect. Tolerant of some exposure to coastal conditions, it is also planted for erosion control and as a windbreak.^[11] Unlike many Australian native plants, it is relatively tolerant of phosphates to some degree in cultivation.^[12]

References

^ ^a ^b "Allocasuarina humilis". Australian Plant Census. Retrieved 7 June 2023.
^ ^a ^b ^c "Allocasuarina humilis". FloraBase. Western Australian Government Department of Biodiversity, Conservation and Attractions.
^ ^a ^b "Allocasuarina humilis". Australian Biological Resources Study, Department of Agriculture, Water and the Environment: Canberra. Retrieved 8 June 2023.
^ Holliday, Ivan (1989). A Field Guide to Australian Trees. Melbourne: Hamlyn Australia. p. 44. ISBN 0-947334-08-4.
^ "Casuarina humilis". APNI. Retrieved 8 June 2023.
^ Otto, Christoph F.; Dietrich, Albert G. (1841). Allgemeine Gartenzeitung. Vol. 9. Berlin. p. 163. Retrieved 8 June 2023.
^ "Allocasuarina humilis". APNI. Retrieved 8 June 2023.
^ Johnson, Lawrence A.S. (1982). "Notes on Casuarinaceae II". Journal of the Adelaide Botanic Gardens. 6 (1): 75. Retrieved 8 June 2023.
^ William T. Stearn (1992). Botanical Latin. History, grammar, syntax, terminology and vocabulary (4th ed.). Portland, Oregon: Timber Press. p. 427.
^ Steane, Dorothy A.; Wilson, Karen L.; Hill, Robert S. (2003). "Using matK sequence data to unravel the phylogeny of Casuarinaceae" (PDF). Molecular Phylogenetics and Evolution. 28 (1): 47–59. doi:10.1016/S1055-7903(03)00028-9. PMID 12801471. Retrieved 12 November 2010.
^ Elliot, Rodger W.; Jones, David L.; Blake, Trevor (1985). Encyclopaedia of Australian Plants Suitable for Cultivation: Vol. 2. Port Melbourne: Lothian Press. p. 483. ISBN 0-85091-143-5.
^ Lullfitz, George. A new image for West Australian plants. p. 46. ISBN 0-9581346-0-X.