Trees of Ojai – Quercus lobata – Valley oak

The Ojai Valley is blessed with several native tree species, some of which grow to become large and iconic. Among those, three in particular stand out: valley oak (Quercus lobata), coast live oak (Q. agrifolia), and western sycamore (Platanus racemosa). This post describes the valley oak and its place in the Ojai Valley.

The valley oak is the largest growing and longest-lived oak tree native to the US. It can grow to over 70 feet tall with an equal or greater spread. Trunk diameters of four feet or more are not uncommon. The species can live 400-600 years. Valley oak is deciduous, losing most of its leaves by mid-January. It has unusually large acorns which normally fall in October, as well as deeply lobed rounded leaves.

Valley oak is endemic to California and its natural range extends from LA County in the south to beyond Redding in the north. It is considered to be a “near threatened” species on the IUCN Redlist, and its numbers are declining statewide.

The Ojai Valley is an especially fine setting for this majestic oak due to our rich soils and readily available groundwater. This oak provides food, habitat, roosting, and nesting for many bird species in Ojai. There are myriad insects that rely on the oak, as well as squirrels and various other “critters”.

In the Ojai Valley we have many valley oaks. Some are in the public right-of-way, including in the streets. Many more are in peoples’ yards and in natural undeveloped areas. Local concerns include infringement by development, varying groundwater levels, improper pruning, poor decisions when planting new trees, and the safety of the trees.

The City of Ojai as well as Ventura County have taken measures to protect these and other oaks in the Ojai Valley during development. Permits are required to remove oak trees or to develop near them. Mitigation may be required for oaks that are removed, as well as measures to protect oaks not being removed.

Valley oaks utilize groundwater and generally occur where groundwater levels are favorable. During extreme drought, groundwater levels may drop precipitously, causing water stress. These trees may survive periodic droughts, but if extreme droughts such as we experienced recently become more common it may affect their survivability over the long term.

Pruning oaks requires a permit in many cases. Poor pruning may damage these oaks to the extent that their longevity and/or safety are impaired. It is important when pruning oaks that the proper permits are obtained, and that only highly qualified contractors are hired to do the work. I recently helped a resident obtain a permit to remove a large valley oak that had been damaged so badly by poor pruning that there was no way to ensure its future safety.

When valley oaks are planted a great deal of thought needs to go into their location. These trees become massive and need plenty of room to grow. Some locations, such as small sidewalk cutouts along City streets, or under utility lines are not appropriate for these large trees. With trunks reaching 3-4 feet in diameter and heights of 70+ feet, a tree planted in such a confined space is doomed to be prematurely removed.

Finally, since these trees become so large, safety is a potential issue. The loss of a large limb above a street or home can be disastrous. Proper evaluation of safety and careful pruning over the years can help to reduce failures.

We are blessed to live among such magnificent oaks and hopefully with proper stewardship they will remain a vital enhancement of our community!

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