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Grevillea robusta
Grevillea robusta

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Zone
Zones 8, 9, 12-27, H1, H2
Full Sun
Full
Minimal Water
Minimal

Grevillea robusta

Silk Oak
Proteaceae
Trees

GREVILLEA

This plant group generally has fine-textured foliage and long, slender, curved flowers, usually borne in dense clusters. Many cannot tolerate salt-laden soils, poor water quality, heavy summer irrigation, or heavy frost, but all are attractive enough to warrant some risk taking. Like other members of the protea family, they are sensitive to high levels of phosphorus in the soil. Fertilize lightly and avoid high-phosphorus fertilizers.

Grevillea robusta

Fast-growing tree to 50–60 ft. (rarely 100 ft.) tall. Young trees are symmetrical and pyramidal. Old ones are broad topped (30–35 ft. wide), usually with a few heavy, horizontal limbs; picturesque against the skyline. Ferny leaves are golden green to deep green above, silvery beneath. Heavy leaf fall in spring, sporadic leaf drop throughout the year. Large clusters of bright golden orange flowers in early spring. Orioles and hummingbirds like the nectar. 

Wood is brittle and easily damaged in high winds. For sturdier branches, cut back the central leader hard at planting time and shorten branches to a well-balanced framework. Thrives in heat; one of the lushest greens for low desert. Useful as a quick, tall screen; can be clipped as a tall hedge. Full sun. Grows in poor, dense soils if not overwatered; can take regular water in fast-draining soils. Young trees are damaged at 24°F/–4°C; older ones are hardy to 16°F/–9°C. Beyond the hardiness range, is sometimes grown as a potted plant or houseplant and discarded when it gets too big.

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