Mystery Tree: Grevillea robusta
Photo: Rick J. Pelleg, 2005.
The tree we saw during our Wild Woodlands programs on April 25 and 26 is a silky oak (Grevillea robusta), sometimes also referred to as a silver oak. It is native to Australia and is a member of the protea family. It is not in the oak family but got its common name from the oak-like grain of its wood.
Height: 15 – 40 m
Leaves: 10 – 30 cm long; 9 – 15 cm wide; bi- or tri-pinnately compound, making it fern-like in appearance; alternate on the stem; dark green with grayish-white or rusty undersides; leaves tend to be variable within the species.
Flowers: large, showy, gold to orange-yellow flowers; held in pairs on racemes (a type of stem) 7.5 to 10 cm long; each individual flower is slender and about 2.5 cm long; bottlebrush-like shaped; require summer heat to flower so those planted in San Francisco often do not flower.
Fruit/Seeds: a pod-like follicle, 20 mm in diameter, is slightly flattened and has a long-curved style; hard, dark-brown to black follicle splits open in late fall releasing the one or two seeds it contains; seeds are about 10 mm long, flattened, and surrounded by a membranous wing.
Further information:
- http://plants.usda.gov/java/profile?symbol=GRRO
- http://hort.ufl.edu/trees/GREROBA.pdf
- McClintock, Elizabeth. The Trees of Golden Gate Park and San Francisco. Berkeley, CA: Heyday Books, 2001.
- Olde, Peter & Marriott, Neil. The Grevillea Book. Vol. 3. Portland, OR: Timber Press, 1995.
- Rodd, Tony & Stackhouse, Jennifer. Trees: A Visual Guide. Berkeley: University of California Press, 2008.
Cutting one of these up for firewood, after just felled, I got a very severe skin reaction from the sawdust. Took about 3 weeks for blisters to be replaced with new skin. Itching remained for another 3 weeks.
Comment by Ross — February 16, 2010 @ 2:48 pm
That is awful. I had not realized that these plants were common allergens until you mentioned it. Here are a few websites from Australia and New Zealand where many grevillea species are common that talk about reactions to grevilleas:
http://asgap.org.au/APOL2009/mar09-s1.html
http://www.dermnet.org.nz/dermatitis/plants/grevillea.html
Comment by nature — February 17, 2010 @ 10:24 am