Grevillea robusta
| Grevillea robusta subsp. var. | Silk oak, Silky oak | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Grevillea robusta, commonly known as the southern silky oak or Silky-oak, or Australian Silver-oak, is the largest species in the genus Grevillea. 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. It is a fast growing evergreen tree, between 18-35 m tall with dark green delicately dented bipinnatifid leaves reminiscent of a fern frond. It is the largest plant in the Grevillea genus, reaching diameters in excess of one metre. These leaves are generally 15-30 cm long with greyish white or rusty undersides. Its flowers are golden-orange bottlebrush-like blooms, between 8-15 cm long, in the spring, on a 2-3 cm long stem and are used for honey production. 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.
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 about −8 °C (17 °F)[1]. 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 flowers and fruit contain toxic hydrogen cyanide.[2] Tridecylresorcinol in G.robusta is responsible for contact dermatitis.[3]
| Standard Cyclopedia of Horticulture |
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Grevillea robusta, Cunn. Silk Oak. One of the most popular of all fern-leaved pot-plants. When young (from 2-5 ft. high) it makes a most graceful subject. In glasshouses it is not grown to large plants, and, therefore, little is known of the great size which it attains in its native forest. According to Von Mueller, it is "indigenous to the subtropical part of E. Austral., rising to 150 ft., of rather rapid growth, and resisting drought to a remarkable degree; hence one of the most eligible trees even for desert culture, though naturally a sylvan plant. The wood is elastic and durable, valued particularly for staves of casks, also for furniture. The richly developed golden yellow trusses of fls. attract honey-sucking birds and bees through several months of the year. The seeds are copiously produced and germinate readily. Rate of growth in Victoria, 20-30 ft. in 20 years. In Ceylon it attained a stem- circumference of 5 ft. in 8 years." In Calif, and S. Fla. it is a street lawn tree, although the branches break easily in exposed places. When grown in the open, it will stand some frost. As a glasshouse plant it is grown almost wholly from seeds, and is used in its young state; as the plant becomes old, it loses its leaves and becomes ragged below. It thrives in the temperature suited to geraniums or roses, and it stands much hard usage and neglect. It is popular as a window subject. Best results with grevillea are usually secured by raising a fresh stock every year, from seed sown late in winter or in spring. The following winter or spring they will be in 4-6 in. pots, and will be in their prime. The young plants need frequent repotting to keep them in good condition. Grevillea robusta has come to be generally known as a florists' plant within the past thirty years. Lvs. twice-pinnatifid (or the pinna deeply pinnatifid), or nearly 3-pinnate under cult., the ultimate divisions narrow and pointed and sometimes lobed, pubescent: racemes 3—4 in. long, solitary or several together on short leafless branches of the old wood; fls. orange, glabrous, the tube ¼ in. long, the parts revolute: fr. about ¾ in. long, broad, very oblique. B.M. 3184. G.2:615; 8:680. G.L. 24:40. A.G. 14:115. A.F. 4:413.—In the W. Indies the plant is much grown, and it is often trimmed to desired shape. In exposed places the foliage becomes golden in cast. Var. compacts, Hort., is a condensed dwarf form with handsome foliage, G.C. III. 49:375. G.M. 54:452. G. 33:393. F. E. 31:1259. Var. pyramidalis, Hort., is offered abroad. Var. F6rsteri (G. forsteri, Hort.) is a form of G. robusta. It has silvery foliage, large trusses of deep bright red fls., and much stronger growth. R.B. 24:3. CH
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Species
Gallery
photo 1
Trunk bark
Leaf
Flowering branches
Flowers
Unripe seed pods
Leaves and dry seed pods
Dry seed pod
Seed pod and seeds
References
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
External links
- w:Grevillea robusta. Some of the material on this page may be from Wikipedia, under the Creative Commons license.
- Grevillea robusta QR Code (Size 50, 100, 200, 500)
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