Skip to content

Landmarks Focus: Oak Restoration in Weir Canyon

PicturePlanting Oak trees in Weir Canyon

OC Parks Weir Canyon Nature Preserve contains an abundance of rare habitats and wildlife, including one of the largest intact coast live oak woodlands in Orange County, making it one of the most ecologically important areas on the Irvine Ranch Natural Landmarks.  This area is admired year-round by hikers, bikers, and nature enthusiasts alike.  But this sanctuary is also under threat. 

The Gold Spotted Oak Borer Beetle, or GSOB for short, is an invasive tree pest that has been documented within Weir Canyon.  Native to southeastern Arizona, it is thought that the beetle first traveled to southern California through infested firewood.  This tiny beetle disrupts and depletes the ability of trees to take up nutrients by laying its eggs on the bark of the trees. The larvae then burrow beneath the bark to feed, and eventually kill the tree.

However, Irvine Ranch Conservancy staff, in partnership with OC Parks and the California Department of Fish and Wildlife, are hard at work to stop the spread of this invasive tree pest.  To further improve the health of the Canyon, conservancy staff began an oak restoration project, funded by California Department of Fish and Wildlife Local Assistance Grant Funds, to replace trees that have been removed due to the GSOB infestation in Weir Canyon.  

To date, nearly 1,200 sets of acorns have been planted with the hope that they will one day become shady oaks. Volunteers and staff monitored light and temperature and used satellite imagery to pick the best areas to plant the new oak trees. Volunteers helped collect and prepare acorns, placed them in holes surrounded by wire baskets to protect them from rodents, and waist-high plastic tubes on top to protect new seedlings from herbivores.  The goal is to provide the best conditions for the young trees to grow and thrive, allowing Weir Canyon to recover from the GSOB infestation.

Following the Canyon 2 Fire, Weir Canyon Nature Preserve was closed to give the plants and animals the time and space they need to recover.  However, these areas have recently been reopened for guided activities.  Make sure to sign up on LetsGoOutside.org today so you can take in the beauty of Weir Canyon and its majestic oak trees.