grass tree

Xanthorrhoea
X. semiplana
Scientific classification
Kingdom: Plantae (unranked): Angiosperms (unranked): Monocots Order: Asparagales Family: Xanthorrhoeaceae Dumort. Genus: Xanthorrhoea Sol. ex Sm.
Species
see text

Xanthorrhoea is a genus of flowering plants native to Australia and a member of family Xanthorrhoeaceae. The Xanthorrhoeaceae are monocots, part of order Asparagales. There are 28 species and five subspecies of Xanthorrhoea.^[1]

Description

The "trunk" of Xanthorrhoea is really just a hollow ring of accumulated leaf bases. Nutrient transport is via aerial roots that run down the centre.

All are perennials and have a secondary thickening meristem in the stem. Many, but not all, species develop an above ground stem. 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. Flowers are borne on a long spike above a bare section called a scape, the total length can be up to four metres long in some species. Flowering occurs in a distinct flowering period, which varies for each species. Flowering can be stimulated by bushfire, in which case it occurs in the next flowering period after the fire.

It is commonly believed that the Xanthorrhoea grow at a rate of about an inch (2½ cm) per century. Xanthorrhoea do grow very slowly, but this is a gross underestimate: after an initial establishment phase the average rate of growth varies for each species but can be as high as about 2½ cm per year. Thus a five-metre tall member of one of the fastest growing Xanthorrhoea would be about 200 years old. A slow one may have a lifespan of 600 years.

Cultivation

Xanthorrhoea may be cultivated, as seed is easily collected and germinated. Whilst they do grow slowly, quite attractive plants with short trunks (10 cm) and leaf crowns up to 1.5 m (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. Most Xanthorrhoea sold in nurseries 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, which may take 3-4 years to die. The most successful examples of transplanting have been where a substantial amount of soil (> 1 cubic metre) has been taken with the plants.

Common names

The best known common name for the Xanthorrhoea is blackboy. This name refers to the purported similarity in appearance of the trunked species to an Aboriginal boy holding an upright spear. Some people now consider this name to be offensive, or at least belonging to the past, preferring instead grasstree, or in the South West the Noongar name balga for X. preissei. In South Australia it is commonly known as yakka, also spelled yacca and yacka. This probably is from a South Australian Aboriginal language,^[2] mostly likely Kaurna.

Traditional Aboriginal uses

Xanthorrhoea is important to the Aboriginal people who live where it grows. The flowering spike makes the perfect fishing spear. It is also soaked in water and the nectar from the flowers gives a sweet tasting drink. In the bush the flowers are used as a compass. This is because flowers on the warmer, sunnier side of the spike (usually the north facing side) often open before the flowers on the cooler side facing away from the sun.^[3]

The resin from Xanthorrhoea plants is used in spear-making^[4] and is an invaluable adhesive for Aboriginal people, often used to patch up leaky coolamons (water-containers) and even yidaki (didgeridoos).

Similar plants

• Kingia and Dasypogon are unrelated Australian plants with a similar growth habit to Xanthorrhoea. Both genera have at times been confused with xanthorrhoeas and mis-named as grasstrees. Some plant classification systems such as Cronquist^[5] have included a wide range of other genera in the same family as Xanthorrhoea. However, later anatomical and phylogenetic research has supported the view of Dahlgren^[6] who regarded Xanthorrhoea as the sole member of the family Xanthorrhoeaceae.

Species

Xanthorrhoea australis flower spike, flowering

Flower spike, after fruiting

• Xanthorrhoea acanthostachya
• Xanthorrhoea acaulis
• Xanthorrhoea arborea
• Xanthorrhoea arenaria
• Xanthorrhoea australis
• Xanthorrhoea bracteata
• Xanthorrhoea brevistyla
• Xanthorrhoea brunonis
• Xanthorrhoea caespitosa
• Xanthorrhoea concava
• Xanthorrhoea drummondii
• Xanthorrhoea fulva
• Xanthorrhoea glauca
• Xanthorrhoea gracilis
• Xanthorrhoea johnsonii
• Xanthorrhoea latifolia
• Xanthorrhoea macronema
• Xanthorrhoea malacophylla
• Xanthorrhoea media
• Xanthorrhoea minor
• Xanthorrhoea nana
• Xanthorrhoea platyphylla
• Xanthorrhoea preissii
• Xanthorrhoea pumilio
• Xanthorrhoea quadrangulata
• Xanthorrhoea reflexa
• Xanthorrhoea resinifera (also called Xanthorrhoea hastilis)
• Xanthorrhoea semiplana
• Xanthorrhoea thorntonii

See also

• Kingia

References

External links

Wikimedia Commons has media related to: Xanthorrhoea

• Xanthorrhoea australis - R.Br. Plants For A Future
• XANTHORRHOEA INFORMATION PAGE Monica Pawlan
• "Xanthorrhoea". FloraBase. Department of Environment and Conservation, Government of Western Australia. http://florabase.dec.wa.gov.au/browse/profile/21189. 
• Xanthorrhoea, Australian Plant Name Index (APNI)