Silkoak or Silk Oak (Grevillea robusta), is a native Australian tree that grows quite well here in Tucson gardens. It has not naturalized in Arizona as it has in Hawaii or Florida because it requires a bit more water than desert natives, although it is drought-tolerant. Silk Oak is hardy to 17 °F (-8.3 °C).
The leaves on this member of the Protea family are large and fern-like, and the flowers are a brilliant yellow-orange. This tree is technically evergreen as it always has leaves, but there is a yearly leaf drop, so it can be a bit messy. These trees are fairly fast-growing and can reach 100 feet (30.5 m) at maturity.
This blooming tree is a bird-watcher's delight, and I highly recommend growing it if you like watching birds from your garden. When they are flowering in the springtime, these trees attract the most colorful of birds like orioles, grosbeaks, tanagers, warblers, and hummingbirds. The flowers are not only filled with sweet nectar, they also attract numerous insects, and both are enjoyed by a wide variety of hungry birds.