Grevillea robusta A. Cunningham ex R. Br.
IUCN
NCBI
EOL Text
"Native of Australia, widely cultivated as a shade tree in the hilly areas."
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| Rights holder/Author | Keystone Foundation, India Biodiversity Portal |
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Where planted in pure stands in Hawaii, silk-oak maintains its purity with little woody competition. In naturalized stands, it grows in association with many other tree species including the native koa (Acacia koa), 'ohi 'a (Metrosideros collina), and introduced species such as tropical ash (Fraxinus uhdei), jacaranda (Jacaranda mimosifolia), molucca albizzia (Albizia falcataria), black-wattle (Acacia decurrens), Christmas-berry (Schinus terebinthifolius), and guava (Psidium guajava).
Planted as a shade tree in coffee and tea plantations.
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| Rights holder/Author | Keystone Foundation, India Biodiversity Portal |
| Source | http://indiabiodiversity.org/species/show/229827 |
"
Global Distribution
Native of East Australia; now common in tropics and subtropics
Indian distribution
State - Kerala, District/s: All Districts
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The oleander pit scale, Asterolecanium pustulans Cockerell, was so damaging in Puerto Rico that further planting of the species was discouraged (7). Amphichaeta grevilleae is a serious leaf spot and defoliating disease in India where it kills young plants (14). Also in India, a serious dieback is caused by a fungus, Corticium salmonicolor (8). No serious primary insects or diseases of the species have been noted in Hawaii, although severe dieback, believed caused by drought, is common on most droughty sites.
Grevillea robusta is a popular ornamental because of its fernlike foliage even in areas where it does not flower abundantly, such as California and Florida north of Miami. In more tropical climates its showy flowers cause it to be widely used.
It has been planted extensively in India and Sri Lanka as shade for tea, and in Hawaii, India, and Brazil to some extent as shade for coffee (2,12,14,16). It is frequently used as a windbreak, although opinions differ as to its wind firmness and branch-shedding tendencies (2). Silk-oak is an important honey tree in India where it is also regarded as a good fuelwood producer (13).
The tree produces an attractively figured, easily worked wood, which was once a leading face veneer in world trade, where it was marketed as "lacewood." The wood contains an allergen that causes dermatitis for many people (15).
"Maharashtra: Ahemdnagar, Dhule, Kolhapur, Satara, Sindhudurg Karnataka: Chikmagalur, Hassan, Mysore Kerala: All districts Tamil Nadu: All districts"
Silk-oak is classed as very intolerant of shade. In Australia, seedlings do not survive beneath closed pure stands of the species because of some substance toxic to them that is produced by or associated with roots of the trees (18). This substance is specific to silk-oak seedlings, causing rapid chlorosis, blackening, and death of seedlings soon after they emerge and begin to grow. Consequently, the tree is nongregarious in its natural habitat. The toxic substance has not been investigated in Hawaii, but it has been observed that reproduction is lacking within dense stands or directly beneath individual trees.
In Hawaii, silk-oak has been planted in mixture with numerous other species. Two of the species it dominates when in mixture are melaleuca (Melaleuca quinquenervia) and horsetail casuarina (Casuarina equisetifolia). Three that grow well in mixture with it are Australian toon (Toona ciliata var. australis), tropical ash, and koa. Three that dominate silk-oak are Norfolk-Island-pine (Araucaria heterophylla), saligna eucalyptus (Eucalyptus saligna), and robusta eucalyptus (E. robusta).
In Brazil, several spacing studies indicated that at 2 years, a spacing of 1 by 3 in (3 by 10 ft) resulted in the best height growth, but at 6 years, 2 by 2 in (6 by 6 ft) was best, with thinning planned at age 10 or 15 (Viega 1958 as cited in 2). In Brazil, an attempt is made to maintain a basal area of 49 to 61 m²/ha (213 to 265 ft²/acre) throughout the life of the stand. In Hawaii, silk-oak has always been planted at a spacing of 3 by 3 in (10 by 10 ft) and left untended. In Uganda experiments, a number of thinnings were made at various ages, but with little apparent effect on mean annual diameter increment (4).
Grevillea robusta, commonly known as the southern silky oak or silky oak, or Australian silver oak, is the largest species in the genus Grevillea of the family Proteaceae. It is not closely related to the true oaks, Quercus. It is a native of eastern coastal Australia, in riverine, subtropical and dry rainforest environments receiving more than 1,000 mm per year of average rainfall.
Contents
Description[edit]
It is a fast-growing evergreen tree, between 18–35 m (59–115 ft) tall, with dark green delicately dented bipinnatifid leaves reminiscent of a fern frond. It is the largest plant in the Grevillea genus, reaching trunk diameters in excess of 1 m (3 ft). The leaves are generally 15–30 cm (6–12 in) long with greyish white or rusty undersides.
Its flowers are golden-orange bottlebrush-like blooms, between 8–15 cm (3–6 in) long, in the spring, on a 2–3 cm long stem and are used for honey production. Like others of its genus, the flowers have no petals, instead they have a long calyx that splits into 4 lobes.[1] The seeds mature in late winter to early spring, fruiting on dark brown leathery dehiscent follicles, about 2 cm long, with one or two flat, winged seeds.
Uses[edit]
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Before the advent of aluminium, Grevillea robusta timber was widely used for external window joinery, as it is resistant to wood rot. It has been used in the manufacture of furniture, cabinetry, and fences. Owing to declining G. robusta populations, felling has been restricted.
Recently G. robusta has been used for side and back woods on guitars made by Larrivée and others, because of its tonal and aesthetic qualities.
Cultivation[edit]
When young it can be grown as a houseplant where it can tolerate light shade, but prefers full sun as it grows best in warm zones. If planted outside, young trees need protection on frosty nights. Once established it is hardier and tolerates temperatures down to −8 °C (18 °F).[2] It needs occasional water but is otherwise fairly drought-resistant.
Grevillea robusta is often used as stock for grafting difficult-to-grow grevilleas.
Care needs to be taken when planted near bushland as it can be weedy.
The tree has been planted widely throughout the city of Kunming in south-western China forming shady avenues.
This plant has gained the Royal Horticultural Society's Award of Garden Merit.[3]
G. robusta is also grown in plantations in South Africa[4] and can also be grown alongside maize in agroforestry systems.[5]
Toxicity and allergic reactions[edit]
The flowers and fruit contain toxic hydrogen cyanide.[6] Tridecylresorcinol in G.robusta is responsible for contact dermatitis.[7]
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Silky Oaks planted in a tea garden
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Trunk bark
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Leaf
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Flowering branches
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Flowers
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Unripe seed pods
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Leaves and dry seed pods
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Dry seed pod
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Seed pod and seeds
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Flowering branches
References[edit]
- ^ RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN 1405332964.
- ^ "Garden Guides: Silkoak".
- ^ "Grevillea robusta AGM". RHS Plant Finder. Royal Horticultural Society. Retrieved 27 July 2013.
- ^ Overseas-grown Australian Timber Species Retrieved on 8 December 2008
- ^ Jackson, N. (2000). "Tree pruning as a means of controlling water use in an agroforestry system in Kenya". Forest Ecology and Management 126 (2): 133–152. doi:10.1016/S0378-1127(99)00096-1.
- ^ Everist, S.L., Poisonous Plants of Australia, Angus & Robertson, 1974.
- ^ Menz, J., Rossi, R., Taylor, W.C, Wall, L., Contact dermatitis from Grevillea'Robyn Gordon', Contact Dermatitis, Vol. 15, Iss. 3, pp 126-131, Apr 2006
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| Source | http://en.wikipedia.org/w/index.php?title=Grevillea_robusta&oldid=637429130 |
Silk-oak is native to coastal eastern Australia from the Clarence River, New South Wales, to Maryborough, Queensland, and is now naturalized in Hawaii and southern Florida (3,16). It was introduced into Hawaii about 1880 and is found on all islands where it reproduces prolifically in certain leeward grassland locations. Although a nongregarious tree in its native habitat, it grows well in pure plantations in Hawaii (18). It is common as an ornamental in Hawaii, Florida, California, and Puerto Rico (5). Because of its prolific reproduction, it has been classed a noxious weed on ranchland in Hawaii (9). In the tropical highlands of India, where it has also been extensively planted, it is often an undesirable escapee from cultivation (13).