Nature’s Notebook

Connecting People with Nature to Benefit Our Changing Planet

You are here

Photo for species Quercus_lobata

Valley oak acorns generally fall in October and are eaten by many species of mammals and birds.  The acorns are often eaten by bruchid beetles.  Valley oaks can have large galls on their twigs and leaves made by small wasps. They can tolerate wildfire and hybridize often with other oak species.

Photo Credit:
© KP Botany via Wikimedia Commons

Quercus lobata

valley oak, California white oak
What does this species look like?
What does this species look like?: 

This tree is deciduous and requires access to groundwater to survive.  It can be over 30 meters tall and the trunk can be 2-3 meters wide. The light grey bark has a texture reminiscent of alligator hide.  When trees are very old, the branches get droopy.  The deeply lobed leaves are rounded and 5 to 12 centimeters long. The shiny leaves are dark green in color and pale green with soft fuzz on their underside.

Quercus lobata is found on slopes and in valleys at elevations less than 1700 meters. They are endemic to California and present in the North Coast Ranges, Cascade Range Foothills, Sierra Nevada Foothills, Tehachapi Mountain Area, Great Central Valley, San Francisco Bay Area, South Coast Ranges, northwest South Coast, Channel Islands, Western Transverse Ranges, and west San Gabriel Mountains.

Where is this species found?
States & Provinces: 
CA
Which phenophases should I observe?
Leaves

Do you see...?

Breaking leaf buds
One or more breaking leaf buds are visible on the plant. A leaf bud is considered "breaking" once a green leaf tip is visible at the end of the bud, but before the first leaf from the bud has unfolded to expose the leaf stalk (petiole) or leaf base.

How many buds are breaking?

Less than 3;3 to 10;11 to 100;101 to 1,000;1,001 to 10,000;More than 10,000

More...

Leaves
One or more live, unfolded leaves are visible on the plant. A leaf is considered "unfolded" once its entire length has emerged from a breaking bud, stem node or growing stem tip, so that the leaf stalk (petiole) or leaf base is visible at its point of attachment to the stem. Do not include fully dried or dead leaves.

What percentage of the potential canopy space is full with leaves? Ignore dead branches in your estimate of potential canopy space.

Less than 5%;5-24%;25-49%;50-74%;75-94%;95% or more

More...

Increasing leaf size
A majority of leaves on the plant have not yet reached their full size and are still growing larger. Do not include new leaves that continue to emerge at the ends of elongating stems throughout the growing season.

What percentage of full size are most leaves?

Less than 25%;25-49%;50-74%;75-94%;95% or more

More...

Colored leaves
One or more leaves show some of their typical late-season color, or yellow or brown due to drought or other stresses. Do not include small spots of color due to minor leaf damage, or dieback on branches that have broken. Do not include fully dried or dead leaves that remain on the plant.

What percentage of the potential canopy space is full with non-green leaf color? Ignore dead branches in your estimate of potential canopy space.

Less than 5%;5-24%;25-49%;50-74%;75-94%;95% or more

More...

Falling leaves
One or more leaves are falling or have recently fallen from the plant. More...

Flowers

Do you see...?

Flowers or flower buds
One or more fresh open or unopened flowers or flower buds are visible on the plant. Include flower buds or inflorescences that are swelling or expanding, but do not include those that are tightly closed and not actively growing (dormant). Also do not include wilted or dried flowers. For Quercus lobata, the male inflorescence is a catkin which is initially compact and stiff, but eventually unfolds to become longer and hang loosely from the branch. Female flowers are very small and petal-less, emerging from the growing stem at the point where a new leaf is attached.

How many flowers and flower buds are present? For species in which individual flowers are clustered in flower heads, spikes or catkins (inflorescences), simply estimate the number of flower heads, spikes or catkins and not the number of individual flowers.

Less than 3;3 to 10;11 to 100;101 to 1,000;1,001 to 10,000;More than 10,000

More...

Open flowers
One or more open, fresh flowers are visible on the plant. Flowers are considered "open" when the reproductive parts (male stamens or female pistils) are visible between or within unfolded or open flower parts (petals, floral tubes or sepals). Do not include wilted or dried flowers. For Quercus lobata, the male flowers will open once the initially compact catkin has unfolded and is hanging loosely. Female flowers are open when the pistils are visible, but will be very difficult to see where they are out of reach.

What percentage of all fresh flowers (buds plus unopened plus open) on the plant are open? For species in which individual flowers are clustered in flower heads, spikes or catkins (inflorescences), estimate the percentage of all individual flowers that are open.

Less than 5%;5-24%;25-49%;50-74%;75-94%;95% or more

More...

Pollen release
One or more flowers on the plant release visible pollen grains when gently shaken or blown into your palm or onto a dark surface.

How much pollen is released?

Little: Only a few grains are released.;Some: Many grains are released.;Lots: A layer of pollen covers your palm, or a cloud of pollen can be seen in the air when the wind blows

Fruits

Do you see...?

Fruits
One or more fruits are visible on the plant. For Quercus lobata, the fruit is a nut (acorn), partially covered with a "cap", that changes from green to light brown.

How many fruits are present?

Less than 3;3 to 10;11 to 100;101 to 1,000;1,001 to 10,000;More than 10,000

More...

Ripe fruits
One or more ripe fruits are visible on the plant. For Quercus lobata, a fruit is considered ripe when it has turned light brown.

What percentage of all fruits (unripe plus ripe) on the plant are ripe?

Less than 5%;5-24%;25-49%;50-74%;75-94%;95% or more

More...

Recent fruit or seed drop
One or more mature fruits or seeds have dropped or been removed from the plant since your last visit. Do not include obviously immature fruits that have dropped before ripening, such as in a heavy rain or wind, or empty fruits that had long ago dropped all of their seeds but remained on the plant.

How many mature fruits have dropped seeds or have completely dropped or been removed from the plant since your last visit?

Less than 3;3 to 10;11 to 100;101 to 1,000;1,001 to 10,000;More than 10,000

More...