Grevillea is a genus of trees and mostly shrubs, numbering about 350 species, the large majority of which are native to Australia. Like many other Australian plants, they belong to the Proteaceae family. Many species are known and grown for their spectacular and exotic-looking flowers, but only the largest species, G. robusta is relevant to urban forestry. This species is usually called silk-oak, despite its lack of relation or resemblance to true oaks.
Silk-oak is a large, fast-growing tree native to the East Coast of Australia where it grows to over 100' tall and is an important timber tree. In our area, the cold, dry air might prevent it from reaching its full size, but it seems to grow well nonetheless. It is said to be hardy to the high teens which should allow it to tolerate even historic freezes in our area.
Of the larger trees that can be grown in our area, I think this species has most spectacular floral showing. In late spring silk-oaks often catch my eye even from the highway, and they are even more spectacular up close where their exotic form can be appreciated. Even when not in bloom, their unique leaves and seed pods have ornamental qualities as well.
This species is said to have brittle wood, so it should be planted a good distance away from structures to avoid damage during storms. It is also a problematic invasive species in Hawaii, and has been known to be weedy in other moist subtropical climates as well. There is evidence that it has escaped in California as well, but only sporadically, and I have not seen evidence that it has completed its lifespan or formed dense groves in wild areas yet. The California Invasive Plant Council has judged this species to have a high risk of becoming an invasive species, so it is worth watching carefully.
Silk-oak is a large, fast-growing tree native to the East Coast of Australia where it grows to over 100' tall and is an important timber tree. In our area, the cold, dry air might prevent it from reaching its full size, but it seems to grow well nonetheless. It is said to be hardy to the high teens which should allow it to tolerate even historic freezes in our area.
Of the larger trees that can be grown in our area, I think this species has most spectacular floral showing. In late spring silk-oaks often catch my eye even from the highway, and they are even more spectacular up close where their exotic form can be appreciated. Even when not in bloom, their unique leaves and seed pods have ornamental qualities as well.
This species is said to have brittle wood, so it should be planted a good distance away from structures to avoid damage during storms. It is also a problematic invasive species in Hawaii, and has been known to be weedy in other moist subtropical climates as well. There is evidence that it has escaped in California as well, but only sporadically, and I have not seen evidence that it has completed its lifespan or formed dense groves in wild areas yet. The California Invasive Plant Council has judged this species to have a high risk of becoming an invasive species, so it is worth watching carefully.