Collection location: Howarth Park, Santa Rosa, Sonoma Co., California, USA [Click for map]
Gills and stipe both bleed white when cut. Growing in oak woodland. Left pileus is 8 cm across.
Which field guide are you using, just wondering what steps you are taking to find the species, and where you might be getting lost. There are a lot of Lactarius in CA, each year I keep learning this again… but alnicola is one of the more common ones. The edges of the caps should be smooth, and the gills should be free of stains — along with the golden color, the white latex and viscid cap, these will ID alnicola pretty well.
The two common pale orange Lactarii in California are L. alnicola and L. scrobiculatus (of which there are several varieties). The latex is initially white for both and eventually turns yellow. However, it is a paler yellow in L. alnicola. Also your specimens don’t seem to show any of the spots on the stipe, or scrobiculations. The other test is taste. L. alnicola should be strongly acrid, whereas L. scrobiculatus is only mildly acrid.