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Friday, January 10, 2014

Quercus lobata - Valley Oak

What an awesome tree. Can't believe how beautiful these trees look clothed in leaves or even better just showing the amazing branching structure. Scotts Valley and Ben Lomond  have the added heat that these trees require to prosper. We do have a few in Rio Del Mar but they will not ever get as large as those or the trees seen in the Central Valley.

Growing to 80 feet tall with a broad open spreading crown, these trees have massive branches with fantatic bark. The branching pattern is spectacular, with smaller and smaller branched creating a soft outline at the perimeter.

Leaves are deciduous, simple, alternate, obovate, 2-4" long, half that in width, 7-11 rounded lobes that reach at least half way to the midrib, generally deeper. They are light green on the upper surface, lighter below with trichomes (hairs) on the veins and petiole.  

Stems are light brown, ridged, with small very small buds except the terminals. They also have trichomes, giving the stems a tannish color until they fall off.

Male and female flowers are separated, males in catkins, females just behind the apical growing points. Males are easy to see, female not so.

Fruit is an acorn 1-2" long borne singly or in pairs on a short stalk. Mature the first year. The cap is called an involucre or involucral bracts which are modified leaves surrounding the inflorescence. 

Oaks have lots of cool pests, especially those forming galls. Some galls are round, some are star shaped, but all are very interesting to look at and see a relationship between a tree species and insects. I came across an interesting article about how oak experts have a hard time correctly identifying some of the oaks but the insects that create galls do not and experts using the gall can help identify the oak. Spined Turbin gall wasp on this one.

 Bark is light gray with darker fissures, becoming alligator skin like when old.

Other oaks with rounded lobes. Around here you are not likely to see many others, you might encounter a white oak or a burr oak but they both have much larger leaves.

695 Loma Prieta Dr 
412 Sumner Dr.

Ben Lomond
Highway 9 Scarborough Hardware Ben Lomond

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