oaks

genus Quercus

Member of beech family (family Fagaceae)
dicots (class Magnoliopsida)
flowering plants (subphylum Angiospermae)

Except for extremely rare examples that I don't expect to encounter, there are no other wild species of this genus in the bay area.

CalFlora lists many oaks in the bay area, but for now I will confine this list to the less rare ones (> 50 CalFlora records). See also the related tanoak (Notholithocarpus densiflorus var. densiflorus).

Key features:

bark color
acorn cap scales thin or thick

“Thin” means that the cap conforms closely to the shape of the underlying nut, rather than being distinctly puffed out.

nut shell hairy, woolly, or not inside
leaf shape, colors on top and bottom

“Adaxially convex” means that the leaf is correspondingly abaxially concave.
Be careful when checking the leaf shape because the tip is considered separately. E.g. a leaf that is “roundish” may actually be lanceolate.

The Marin extension of UC Davis provides some of the identification tips below.

red oaks
section Lobatae

acorn cap scales thin, shell hairy to woolly inside, at least at tip
bark dark gray or gray-brown to black
includes the informal group of black oaks: california black oak (Quercus kelloggii), coast live oak (Quercus agrifolia), and interior live oak (Quercus wislizeni)

golden oaks
section Protobalanus

thick acorn cap scales covered in golden hairs
bark a pale gray

white oaks
section Quercus

acorn cap scales generally thick/knobby, glabrous inside
bark light gray to ± white
deciduous

Toxicity of acorn, oak (Quercus spp.):
1 – Skin contact with these plants can cause symptoms ranging from redness, itching, and rash to painful blisters like skin burns.
3 – Ingestion of these plants is expected to cause nausea, vomiting, diarrhea and other symptoms that may cause illness but is not life-threatening.

7 observed taxons / 4 unobserved taxons / 4 keys

Chris’s observations: 73 (37 are research grade)

Locations:

Edgewood Park & Natural Preserve: 12
Castle Rock SP: 5
Henry Coe SP: 5
Almaden Quicksilver CP: 4
Calero CP: 4
Mt. Diablo SP: 4
Sierra Azul OSP: 4
Waterdog Lake & Open Space: 3
Bear Creek Redwoods OSP: 2
Coyote Valley OSP: 2
Long Ridge OSP: 2
Pleasanton Ridge RP: 2
Russian Ridge OSP: 2
Skyline Ridge OSP: 2
Windy Hill OSP: 2
Alum Rock Park, San Jose
Coyote Creek Trail
Coyote Lake / Harvey Bear Ranch CP
Dr. Aurelia Reinhardt Redwood RP
Ed R. Levin CP
Foothills Nature Preserve, Palo Alto
Fremont Older OSP
Huddart CP
Jacks Peak CP
Joseph D. Grant CP
Monte Bello OSP
Mt. Madonna SP
Máyyan 'Ooyákma Coyote Ridge OSP
Pescadero Creek CP
Rancho Cañada del Oro OSP
Sam McDonald CP
Santa Teresa CP
Yosemite NP

Months:

Jan.: 4
Feb.: 1
Mar.: 10
Apr.: 12
May: 7
Jun.: 9
Jul.: 4
Aug.: 1
Sep.: 4
Oct.: 3
Nov.: 13
Dec.: 5

For more details, use advanced search.

Taxon info: iNaturalist – Calflora – Jepson eFlora – FNA

Bay Area species: iNaturalist – Calflora