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Origin and Habitat: Xanthorrhora glauca occurs in large numbers on rocky ranges in southeast Australia.
Habitat and ecology: It is occasionally seen in large communities in woodland on steep edges and sides of gorges, mainly in shallow rich basaltic soils and, at some sites in serpentine soils or sandstone. It is also found in deep coastal sand and hummock grassland with very sparse shrub. The plants are highly fire-resistant and are among the first to resprout after wildfire as the living growth is buried within the old dead leaf bases. The nectar-rich flowers attract many insects. There is some overlap of characters between the subspecies where their distributions abut. Populations on the coastal dunes hybridize with Xanthorrhora fulcra and Xanthorrhora latzfolia in distinct short-range hybrid swarms.
Xanthorrhoea glauca D.J.Bedford
Fl. Australia 46: 226 1986
Xanthorrhoea glauca subs. angustifolia D.J.Bedford
Fl. Australia 46: 226, 165. 1986
ENGLISH: Grass tree, Grey Grass-tree
Description: The grass tree, Xanthorrhora glauca, is an evergreen sword-leaf plant up to 8 m tall with hundreds of very narrow, hard-textured bluish glaucous green leaves radiating from the apex of each branch. It is one of the tallest species in the genus, which grow substantial aboveground stems. This plant has a unique structure, with a true stem of fibrous conducting tissue supported by a sheath of tightly packed old leaf bases glued by a reddish crystalline resin. Tall, rod-like flower spikes grow above the foliage then numerous tiny, white flowers emerge from densely packed, brown bracts. The flower spikes consume much of the plant energy store and may not reappear for several years. Xanthorrhoea glauca is a plant that has a special place in the heart of many Australians. This unusual and iconic plant has been a part of Aboriginal history, colonial artworks and a modern day inspiration to landscape architects. Two sub-species are recognised; subspecies angustifolia and glauca.
Trunk; 1-5 m high, branched or single; crowns 1-many, almost spherical.
Leaves: Spiralled, quadrate-rhombic to narrowly transverse-rhombic in transverse section, 1.3-5.0 mm wide (mostly 3–4 mm wide in var. glauca and 1.3–2.8 mm wide in var. angustifolia), 0.9-2.6 mm thick, blue-green, glaucous (var. glauca) to greyish (angustifolia).
Inflorescence: Dense, spike-like on woody scapes. Scape 0.5-1 m long, 1.8-4.6 cm diam.; spike 1.5-4 times as long as scape, rarely equal to scape, 1-2 m long, rarely to 2.5 m, 3.5-7.7 cm diameter (less than 1.6 m tall, 4–5 cm diameter in var. angustifolia); cluster bracts prominent for most of spike length, ± narrow-tri-angular, subglabrous; packing bracts acute or triangular, subglabrous, rarely glabrous.
Flowers: Actinomorphic, with tepals free. Outer tepals acute to narrow-triangular, beaked, without proboscis, glabrous except hairs on beak. Inner tepals erect to slightly recurved, with proboscis, glabrous except hairs at apex. Beak to 1.5 mm long (0.5 mm long in var. angustifolia)
Blooming season (in habitat): Flowers June-October.
Fruits : Loculicidal capsules.
Subspecies, varieties, forms and cultivars of plants belonging to the Xanthorrhoea glauca group
- Xanthorrhoea glauca D.J.Bedford: mostly 3–4 mm wide in transverse section, 1–2.6 mm thick, blue-green. Spike 100–200 cm long, 4–6 cm diameter. Outer tepals triangular with a beak to 1.5 mm long. South-east Australia.
- Xanthorrhoea glauca subs. angustifolia D.J.Bedford: mostly 1.3–2.8 mm wide in transverse section,, O.9–1.6 mm thick, greyish. Spike 100–160 cm long, 4–5 cm diameter. Outer tepals triangular with a beak to 0.5 mm long.
Bibliography: Major references and further lectures
1) Gwen J. Harden “Flora of New South Wales” Volume 4 New South Wales University Press, Australia., 01 January 1993
2) Tony Rodd, Jennifer Stackhouse “Trees: A Visual Guide” University of California Press, 2008
3) James W. Byng “The Flowering Plants Handbook: A practical guide to families and genera of the world” Plant Gateway Ltd., 16 October 2014
4) Wikipedia contributors. "Xanthorrhoea glauca." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 4 Sep. 2014. Web. 11 Jan. 2015.
5) D. J. Bedford “Xanthorrhoea glauca”. PlantNET - NSW Flora Online, <http://plantnet.rbgsyd.nsw.gov.au> Web. 11 Jan. 2015.
6) Borsboom, A.C. “Xanthorrhoea: A review of current knowledge with a focus on X. johnsonii and X. latifolia, 2 Queensland protected plants-in-trade.” Environmental Protection Agency, Queensland.2005.
7) Spencer, R. “Grassing on the trees.” Australian Horticulture 101(12): 18 2003.
8) Stanley, T.D. & Ross, E.M. “Flora of South-eastern Queensland” Vol. 3. Queensland Department of Primary Industries, Brisbane.1989
9) Wrigley, J.W. & Fagg, M. “Australian Native Plant Cultivation, use in landscaping and propagation” 5 th edition. Reed New Holland Publishing 2003.
10) Samantha Cullen “Xanthorrhoea glauca” Centre for Australian National Biodiversity Research, 2010, Australian National Herbarium, Australian Government, Canberra, <http://www.anbg.gov.au/gnp/interns-2010/xanthorrhoea-glauca.html> Web. 11 Jan. 2015.
Cultivation and Propagation: Xanthorrhoea glauca is a slow growing, carefree and durable plant admired for its spherical form and fine texture and makes it a perfect garden specimen. It is among the Xanthorrhoea species that form a trunk with age and won't be passed over by anyone with an appreciation for sculptural plants. This species is highly tolerant of drought and heat, thrives in well drained, aerated soils that have a low nutrient content, making it an easy plant to include in any garden.
Growth rate: This plant is seldom seen in cultivation due to its slow growth rate. In its natural environment X. glauca is expected to only grow one to two centimetres a year, though it has been suggested that growth rates are greatly increased when grown by seed. Although the slow growth rate has hindered interest in the past this plant gives the gardener satisfaction for decades.
Soil: Plant in very fast draining soil. It is adapted to a hot, dry environment, but has some tolerance to moisture and humidity when planted in a very well-draining soil.
Transplant: This practice is risky as all Xanthorrhoea species are infamous for having sensitive roots. In order to reduce the chance of death a sunny position should be chosen and the soil should be well aerated for best results. When planting into a pot, sand or gravel should be added to improve drainage. When placing out into the garden best results are achieved by planting on top of a mound. All precautions should be taken to reduce the amount of disturbance to roots. Many horticulturalists recommend cutting and slowly pulling away the plastic pot and carefully placing into a pre dug hole that is double the width and depth of the pot. The first few months after planting are a critical time and daily watering should maintained for the first month before being slowly reduced. It can take up to two years for a grass tree to die so any fungal infections should be treated, and any flower spikes should be removed to ensure resources are used to establish new roots.
Waterings: After establishment provide little or no water in winter. Treat like a succulent. However, they grow faster if watered well (don't water the crown, though they rot easily). In the garden they should be placed in a sunny, well-drained area with additional summer water in dry climates.
Exposure: They thrive best in full sun.
Uses: These make great specimen plants for xeriscape gardens and blend well in either tropical or arid gardens. Small plants are relatively inexpensive, but larger ones are a fortune. These make excellent potted specimens, and their symmetrical form provides a striking focal point, ans display wonderful shadows when illuminated by night lighting. In cooler climates they thrive well in gravel garden, as they have proven quite hardy because of the excellent drainage.
Hardiness. Best where winter temperatures stay above 0° C, but is hardy to around -9° C if very dry. Plants in containers can be moved inside during longer cold spells.
Pest and diseases: This plant is not susceptible to many insect infestations.
Maintenance: The leaf bases can be trimmed to expose the trunk or even burnt away depending on the gardener. When the trunk is pruned of the older, lower leaves, the remaining leaf bases create a beautiful symmetrical spiral leaf-base pattern.
Propagation: Easy to propagate from seeds(If available).
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