Native California Walnut Trees in the East Bay

In the summer of 2015, Friends of the Creeks and the Northern California Black Walnut Partnership successfully raised the $10,000 required to collect samples of candidate black walnut trees for genetic testing.  Our deepest gratitude to our 55 donors. Heath Bartosh, local rare plant botanist, has collected the samples and delivered them to UC Davis for testing. Results will be available in the fall. Here are some details:

We were able to take 66 samples, 10% more than the 60 we had planned. Half of them came from the historical core area – 25 from Walnut Creek and 10 from Las Trampas. Another 15 were scattered along the Marsh Creek watershed. Seven more were located in the Alhambra-Carquinez area and five around El Sobrante. Right at the end of the sampling period, we heard about a grove of old trees at Sunol. We sampled one that had been partially cored by a dendrochronologist who estimated it had germinated about 1860.  A few statistics:

   Tallest tree:  El Sobrante, 73 feet
   Largest diameter:  Carquinez, 76.7 inches
   Widest crown:  Sunol, 87 feet; Carquinez, 84


Genetically pure trees will be propagated and used in creek restoration projects in Contra Costa and Alameda  Counties.  We are hoping that our sample will include enough pure natives to provide some seed stock for each major area and adequate genetic diversity overall.  Native walnuts (Juglans hindsii) grow both in creek channels and uplands, so everyone in the East Bay will benefit from having another species to use in their restoration projects.

See a slideshow about the overall project including maps.

Update, August 2016:  More than half the samples are native!  We don't know which ones yet, but we can begin to think about how to undertake propagation and restoration.

large walnut tree

Botanist Heath Bartosh standing at the base of the giant walnut on Carquinez Strait. This and the Sunol tree appear to be the largest and oldest trees in our sample and therefore the best candidates to be genetically pure.