SOLVED: Is this a Valley Oak tree?

Sunnyvale, CA

I passed by these street trees in Sunnyvale, CA all winter and early spring, thinking they were dead because there wasn't a leaf or sign of life on any of them. But look at them now! The leaves are similar in shape to those on a Valley Oak, but I didn't think that Oak trees were deciduous in our warm SF Bay Area climate. I just looked this up on the internet and see that they are deciduous, so I'm guessing that this is a Valley Oak. I know that my Coast Live Oak tree has leaves all year.

This message was edited Jul 27, 2021 1:17 PM

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Scott County, KY(Zone 5b)

Take a look at California Black Oak - Quercus kelloggii.

https://davesgarden.com/guides/pf/go/81457

Scott County, KY(Zone 5b)

Note the bristle tips on the lobes of the leaves. That is indicative of oaks in the Red Oak group. White Oak group have leaves that lack bristle tips on the lobes. Valley Oak (Quercus lobata) is in the White Oak group, and does not have the bristle tips on the lobes.

The trees you've shown could always also be species not native to California, but I suspect that is not normally done in a street tree location like this. If these were planted by local government, you could probably contact the urban forester or city arborist to learn more about their tree planting strategies.

Scott County, KY(Zone 5b)

Being a bit of a Quercophile, and having had the opportunity to visit California a number of times since a tenth anniversary trip in 1997, I would recommend anyone wishing to know their local California oaks better to pick up a text like one of these.

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Sunnyvale, CA

ViburnumValley, you are a master of trees. At least I know know that it's some kind of Quercus rubra. I'll check for fall color, although many of our trees that look red on the East Coast never turn colorful in our warm climate. I have a Red Maple in my front yard ("Bowhall") and the green leaves just turn brown and start falling off in August and September. It's the last tree to get leaves in the spring and the first to drop leaves in late summer/early fall. It's totally bare 6 months out of the years around here in the SF Bay Area.

Scott County, KY(Zone 5b)

Imagine if you lay a fish on your sidewalk...that's probably what that poor Acer rubrum feels like in SF Bay area California - a long way from the northeast Appalachian range.

Please note that I mentioned Red Oak group: that means oak species that are related to Red Oak (Quercus rubra) by characteristics like bristle tips on the leaf lobes. Other California oak species in this group (scientifically referred to as the subgenus Erythrobalanus) include California Black Oak, Interior Live Oak, Coast Live Oak, and Santa Cruz Island Oak.

This is contrasted with the White Oak group (subgenus Lepidobalanus), to which Valley Oak, Blue Oak, Engelmann Oak, Oregon Oak, and host of other California oaks belong.

These groupings indicate evolutionary lineages - oak species that are more like each other than to the species in the other groups. This is another way to narrow down ID possibilities in these similar plants.

An additional note about these groupings: these species will hybridize with others in their group, but not with species outside their group. Since many Quercus sp. are promiscuous and wind-pollinated, this helps sort out who parents could be when a hybrid oak is discovered.

Whether or not colorful foliage runs in Quercus kelloggii genes, you will be able to watch for acorns forming and for the new leaves and catkins emerging in the spring. Those will be characteristics that can help home in on a positive identification.

Here's a chart from Oaks of California:

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