| Xanthorrhoea | |
|---|---|
 | |
| X. semiplana | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Order: | Asparagales |
| Family: | Asphodelaceae |
| Subfamily: | Xanthorrhoeoideae |
| Genus: | Xanthorrhoea Sol. exSm. |
| Species | |
| Synonyms[1] | |
AcoroidesSol. ex Kite, not validly published | |
Xanthorrhoea (/zænθoʊˈriːə/[2]) is agenus of about 30species ofsucculentflowering plants in the familyAsphodelaceae. They areendemic to Australia. Common names for the plants includegrasstree,grass gum-tree (for resin-yielding species),kangaroo tail,balga (Western Australia),yakka (South Australia),yamina (Tasmania, from thepalawa kani language), andblack boy (or "blackboy"). The most common species isXanthorrhoea australis, and some of these names are applied specifically to this species.
All species in the genus areperennials and have asecondary thickeningmeristem in the stem. Many, but not all, species develop an above ground stem. The stem may take up to twenty years to emerge. Plants begin as a crown of rigid grass-like leaves, thecaudex slowly growing beneath. The main stem or branches continue to develop beneath the crown. This is rough-surfaced, built from accumulated leaf-bases around the secondarily thickened trunk. The trunk is sometimes unbranched, some species will branch if the growing point is damaged, and others naturally grow numerous branches.[3][4]
Flowers are borne on a longspike above a bare section called ascape; the total length can be over three to four metres long in some species.[4] Flowering occurs in a distinct period, which varies for each species, and often stimulated bybushfire. Fires will burn the leaves and blacken the trunk, but the plant survives as the dead leaves around the stem serve as insulation against the heat of awildfire.[citation needed]
The rate of growth ofXanthorrhoea is slow. Some species grow slowly (0.8–6 centimetres or 0.31–2.36 inches in height per year), but increase their rate of growth in response to season and rainfall.After the initial establishment phase, the rate of growth varies widely from species to species. Thus, while a five-metre-tall (16 ft) member of the fastest-growingXanthorrhoea may be 200 years old, a member of a more slowly growing species of equal height may have aged to 600 years.[5][4]
Xanthorrhoea is part of the familyAsphodelaceae, containing relatedgenera such asAloe,Alstroemeria,Gasteria,Haworthia andHemerocallis (to name a few), but is placed within its ownmonotypicsubfamily, theXanthorrhoeoideae.[1] The Xanthorrhoeoideae aremonocots, part of the greaterorder ofAsparagales.[6]
A reference to its yellowresin,[2]Xanthorrhoea literally means "yellow-flow" inAncient Greek.Smith named it, in1798,[7] fromxanthos ('yellow, golden') andrhœa ('flowing, flow').[2] The invalidAcoroides ('Acorus-like'[8]) was a temporary designation inSolander's manuscript from hisvoyage with Cook, originally not meant for publication.[7]
Kingia andDasypogon are unrelated Australian plants with a similargrowth habit toXanthorrhoea. Both genera have, at times, been confused with xanthorrhoeas and misnamed as "grasstrees".[citation needed] Some plant classification systems, such asCronquist,[9] have included a wide range of other genera in the same family asXanthorrhoea. However, future anatomical and phylogenetic research supported the views of Dahlgren,[10] whom regardedXanthorrhoea as the sole taxon of the family Xanthorrhoeaceaesensu stricto, which is now treated as a subfamily, Xanthorrhoeoideae.[11]
Common names forXanthorrhoea include grasstree, grass gum-tree (for its resin-yielding species),[2] and kangaroo tail.[12] The namegrasstree is applied to many other plants. They are also known as balga grass plants, which derives from the wordbalga in theNoongar language ofsouth-west of Western Australia, particularly forX. preissii.[13] Its meaning is "black boy" or "blackboy", a name which was applied to the plant for many years. Some thought thatAboriginal peoples used the name balga because the trunk blackened after a bushfire resembles a child-like black figure. The name is now seen as racist, andXanthorrhoea are more commonly known as grass tree.[14][15] However a 2015 report written byAboriginal Tasmanian authors, who refer to the plant asyamina, says "yamina forest onlungtalanana is important to the community. yamina are also commonly known as black boys. They are called this because the plant has a thick black trunk".[16]
InSouth Australia,Xanthorrhoea is commonly known asyakka, also spelledyacca andyacka, a name probably from[13] theKaurna language (Yakko, or alternativelyKurru). TheNgarrindjeri name isBukkup.[17]
Some of the above names are applied specifically toXanthorrhoea australis, the most common species.[18]
The genus is endemic to Australia, occurring in all national states and territories. Some species have a restricted range, others are widely distributed.According to theWorld Checklist of Selected Plant Families, as of September 2014[update] the following species are accepted:[1]
| Image | Name | Authority | States and Territories | ||||||
|---|---|---|---|---|---|---|---|---|---|
| NSW | QLD | VIC | TAS | SA | WA | NT | |||
 | X. acanthostachya | D.J.Bedford | · | · | · | · | · | Y | · |
| X. acaulis | (A.T.Lee)D.J.Bedford | Y | · | · | · | · | · | · | |
 | X. arborea | R.Br. | Y | · | · | · | · | · | · |
| X. arenaria | D.J.Bedford | · | · | · | Y | · | · | · | |
.JPG) | X. australis | R.Br. | Y | · | Y | Y | Y | · | · |
| X. bracteata | R.Br. | · | · | · | Y | · | · | · | |
| X. brevistyla | D.A.Herb. | · | · | · | · | · | Y | · | |
 | X. brunonis | Endl. in J.G.C.Lehmann | · | · | · | · | · | Y | · |
 | X. caespitosa | D.J.Bedford | · | · | · | · | Y | · | · |
 | X. concava | (A.T.Lee)D.J.Bedford | Y | · | · | · | · | · | · |
| X. drummondii | Harv. | · | · | · | · | · | Y | · |
 | X. fulva | (A.T.Lee)D.J.Bedford | Y | Y | · | · | · | · | · |
 | X. glauca | D.J.Bedford | Y | Y | Y | · | · | · | · |
 | X. gracilis | Endl. in J.G.C.Lehmann | · | · | · | · | · | Y | · |
 | X. johnsonii | A.T.Lee | Y | Y | · | · | · | · | · |
 | X. latifolia | (A.T.Lee)D.J.Bedford | Y | Y | · | · | · | · | · |
.jpg) | X. macronema | F.Muell. ex Benth. | Y | Y, Fraser Island | · | · | · | · | · |
 | X. malacophylla | D.J.Bedford | Y | · | · | · | · | · | · |
 | X. media | R.Br. | Y | · | · | · | · | · | · |
 | X. minor | R.Br. | Y | · | Y | · | Y | · | · |
 | X. nana | D.A.Herb. | · | · | · | · | · | Y | · |
 | X. platyphylla | D.J.Bedford | · | · | · | · | · | Y | · |
 | X. preissii (syn.X. pecoris F.Muell.) | Endl. in J.G.C.Lehmann | · | · | · | · | · | Y | · |
 | X. pumilio | R.Br. | · | Y | · | · | · | · | · |
 | X. quadrangulata | F.Muell. | · | · | · | · | Y | · | · |
 | X. resinosa (syn.X. hastilis) | Pers. | Y | · | Y | · | · | · | · |
 | X. semiplana | F.Muell. | · | · | Y | · | Y | · | · |
 | X. thorntonii | Tate | · | · | · | · | Y | Y | Y |
Grasstrees grow in coastal heaths, and wet and dry forests of Australia. They are drought and frost tolerant. The grass tree mainly occurs in soils that are very free draining and consequently low in nutrients. It survives in the poorest soils, with a shallow root system, enabling it easily access nutrients from decaying litter, while storing all the food reserves in its stem.[19]
The grass tree has developed adaptations that help it better suit the environment where it occurs. If a fire breaks out, the grass tree has a special physiological adaptation called thermal insulation that helps protect the plant. The grass tree holds its thick, dead leaves around its stem which serves as insulation, and helps to protect the plant against the heat of the fire.[20]
They need fire to clear away dead leaves and promote flowering, as these slow-growing trees were among the first flowering plants to evolve.[21]Grass trees have developed a structural adaptation which helps the grass tree take advantage of soil fertilized with ash after fire, producing a flowering stalk in the aftermath.[citation needed]
The grass tree forms amycorrhizal relationship with fungi deep in its root system, wherein fungi live in a mutually beneficial relationship with the grass tree roots. The fungus increases the tree root's access to water and nutrients and therefore increases tree growth especially in poor conditions. The grass tree also suffers from a condition known as phytophthora dieback.Phytophthora cinnamomi is a discrete soil borne pathogen that attacks and destroys vascular root systems, causing hosts to perish through lack of nutrients and water. It is spread through infected plants and the movement of contaminated soil and gravel.[22] The leaves of the grass tree are hosts to another fungi,Pseudodactylaria xanthorrhoeae.[23]
Xanthorrhoea may be cultivated, as seed is easily collected and germinated. While they do grow slowly, quite attractive plants with short trunks (10 centimetres or 3.9 inches) and leaf crowns up to 1.5 metres or 4 feet 11 inches (to the top of the leaves) can be achieved in 10 years. The slow growth rate means that it can take 30 years to achieve a specimen with a significant trunk. MostXanthorrhoea sold innurseries are established plants taken from bushland. Nurseries charge high prices for the plants. However, there is a very low survival rate for nursery-purchased plants (mainly due to over watering), which may take several years to die. The most successful examples of transplanting have been where a substantial amount of soil, greater than one cubic metre (35 ft3), has been taken with the plants.[citation needed]
Xanthorrhoea is an iconic plant that epitomizes the Australian bush in its ability to live in poor nutrient soils and respond to wildfire.[24]
Commonly-grown species for the garden includeXanthorrhoea australis,X. malacophylla, andX. preissii.[4]
Xanthorrhoea is important to the Aboriginal peoples. It is a highly-valued resource with many uses.[25] The flowering spike may be utilised as the lightweight handle of a composite spear with a hardwood sharp shaft inserted into the end.[26] It is also soaked in water and the nectar from the flowers gives asweet-tasting drink.[citation needed]
In the bush the flowers could reveal directions, since flowers on the warmer, sunnier side – usually north – of the spike often open before the flowers on the cooler side facing away from the sun.[27]
The resin fromXanthorrhoea plants is used inspear-making[28] and is an invaluable adhesive for Aboriginal people, often used to patch up leakycoolamons (water containers) and even yidaki (didgeridoos). The dried flower stalk scape was also used to generate fire by the hand drill friction method.[citation needed]
On theTasmanian island oflungtalanana, Aboriginal people use the leaves forweaving.[16]
Resin collected from the plant was used in Australia until the mid-twentieth century for the following purposes:[29]
| National | |
|---|---|
| Other | |