Collection location: Los Trancos Preserve, Palo Alto, California, USA [Click for map]
Ok, these are acrid, but not intensely so (not as much as R. cemoricolor say. (I’m getting to much into Russula details, if I am evaluting the intesity of the arcid taste…)). These are fading with only the reddish tones at the margin of the disc. Something like R. silvicola (R. cremoricolor) does develop yellow patches as it ages, or gets heavy rains. But this is not patches, but a even fading to just the margin. Plus the margin is a light pinkish/red perhaps orange/copper tones. This seems to match the discription for R. bicolor. Although the discription states the habitat as spruce forests in north costal regions, but also hardwood forests of the foothills. Are the Santa Cruz mountains foothills? Maybe? There is also the mysterious R. paxilliodes, which was only described from Stanford campus, which isn’t too far away, which will fade to red at the margin… so I don’t know.
But with the pinkish/copper red tones on the margin here, I’ll go with R. bicolor.