Squirrels, Rejoice! The California Black Walnut will Bear Fruit this Fall

Sep 7, 2021 | MSHCP, News, Species

The California Black Walnut is a lush, beautiful tree found throughout southern California. In western Riverside County, this tree grows primarily among Coastal Sage Scrub, Grasslands, and other plants on the Santa Rosa Plateau. It also lives in more densely populated areas like in around the City of Corona.

The species is a low-growing hardwood tree. It prefers drier slopes not prone to flooding or erosion, but it thrives near groundwater and intermittent streams. While wildfires can destroy its surroundings, the California Black Walnut is resilient. Wildfires create bare ground, where sunlight allows seedlings to take root and grow new trees.

From March to May, the tree sprouts new leaves and begins to flower. During this time, the fruit (or walnuts) begins growing once flowers have been pollinated. The walnuts reach full maturity in the fall, attracting squirrels and other foragers for immediate snacking or to save the nuts for winter. Although not as showy as New England’s fall foliage, the California Black Walnut trees can provide a splash of color once summer turns to fall. It produces fruit in the spring, harvest in the fall, and finally goes dormant in the winter.

The California Black Walnut has a typical lifespan of 20-30 years. The tree tends to develop heart rot at this age, and older limbs start to dry out, becoming infested with termites, wood-boring beetles, and fungi and making forage for other insects, birds, and mammals. However, some hardy specimens have lived nearly 100 years.

The species is threatened by urban development and agricultural activity. The California Black Walnut is one of 63 plant species protected by MSHCP. The MSHCP seeks to protect these trees by preserving 6,100 acres of suitable habitat in large blocks. Significant acreage is required so that the California Black Walnut has the opportunity to spread its seedlings.