The red oaks (section Lobatae)
Quercus agrifolia: coast live oak. An evergreen tree typically 30-75 feet tall with smooth grey bark that develops soft splits as it ages, giving a variable appearance from mostly smooth to almost zebra-striped. Leaves: blade 1-2.25 inches long, oval to round, convex, usually with spines at leaf edge, underside of leaves sometimes with "hairy armpits" at junction of midvein and lateral veins. Number of lateral veins usually limited to 3-5 "pair." Acorns: mature in 1 year (unusual for an oak in this section), with pointed tip, cap usually about as deep as wide, covered with scales and little to no hair.
Quercus kelloggii: black oak. A deciduous tree typically under 75 feet tall with smooth grey young bark that becomes deeply furrowed and dark brown to black as it matures. Leaves: blade 3-7 inches long, deeply lobed with soft bristles adorning the lobe ends. Acorns: mature in 2 years with a rounded tip (ignoring the little spine on the end). The acorn cap is generally as deep as it is wide, often covering most of the acorn shell, with scales and little to no hair.
Quercus parvula: Shreve oak. An evergreen tree, typically under 50 feet tall, with smooth grey young bark that eventually furrows to an irregular checkered grey. Leaves: blade 1.5-3.5 inches, mostly flat, oblong to spear tip shaped, generally with a pointy tip, leaf edges somewhat variable, often (but not always) without spines. Undersides of leaves are a dull, hairless, light olive-green, generally with >5 "pair" of lateral veins. Acorns: mature in 2 years, rounded tip (ignoring the little spine on the end). The acorn cap is bowl shaped, usually wider than it is deep, with thin, flat scales.
Quercus wislizeni: Interior live oak. An evergreen tree typically 30-65 feet tall, with smooth grey bark that quickly furrows and checkers to darker grey as it matures. Leaves: blade 1-2 inches long, oblong or oval, usually flat, sometimes with a pointy tip, leaf edges often highly variable, showing spines and teeth on some leaves and not on others. Leaf undersides are normally a shiny(ish) yellow green,hairless, and typically exhibit >5 "pair" of lateral veins. Acorns: mature in 2 years, with a slightly pointed end. Acorn cup is bowl shaped, sometimes as deep as it is wide, with thin, flat scales.
The white oaks (section quercus)
Quercus douglasii: Blue oak. A deciduous tree typically 20-60 feet tall, with grey-brown checkered trunk bark. Leaves: blade 1.5-2.25 inches long, oval, tip rounded, margins wavy or slightly lobed, upper surface a powdery blue-green. Acorns: mature in 1 year, oval in cross-section with a slightly pointed tip. Acorn cup is shallow, wider than deep, and knobby.
Quercus garryana: Oregon white oak. A deciduous tree typically 25-65 feet tall with thin, ridged, greyish-brown bark. Leaves: blade 2-7 inches long, with 5-7 deep lobes, upper surface glossy and somewhat smooth, lower surface dull light green, usually with fine hairs. Acorns: mature in 1 year, oval to almost spherical in cross section with a rounded tip. Acorn cup shallow, wider than deep, and slightly knobby.
Quercus lobata: Valley oak, Roble. A deciduous tree of any size up to about 100 feet tall, with deeply checkered grey-brown bark. Leaves: blade 2-5 inches long, with 6-10 deep rounded lobes. Upper surface somewhat shiny, but typically rougher than
Q. garryana, lower surface pale green with fine hairs. Acorns: mature in 1 year, long and conical in shape, with a pointed tip. Acorn cup often as wide as deep, and typically very knobby.
