This species was described based on a collection made in El Dorado County, California (Thiers 1975).

Leccinum in general are taxonomically confounded by lack of informative morphological criteria, as well as poorly-known and competing species concepts. By virtue of combination of morphology and ecology, this species seems somewhat distinctive, but a pigment abnormality can’t be ruled out given the small number of known collections and lack of genetic data.

L. californicum should be compared genetically with L. montanum; which has a brown to grey brown or cinnamon-brown cap, but otherwise is very similar. It co-occurs with this species at known locations in California (Siegel et al. 2019)

Leccinum californicum is a white to pale buff-capped bolete growing with aspen in the Sierra Nevada mountains of California. This appears to be a rare species; currently known from four high elevation aspen groves. Due to the infrequent and sporadic reports, it is difficult to estimate its full population size or distribution. However, given the relatively small amount of suitable habitat and infrequent number of reports, it can be assumed that the species is rare to uncommon and occurs in a limited number of sites. Conservatively, it is estimated that there are no more than 500 appropriate sites for this species, containing 10-20 mature individuals each with an estimated population size of 5,000-10,000 distributed in these small scattered subpopulations. Its host tree is in decline, and it is inferred that the L. californicum population is decreasing too. Therefore, L. californicum is assessed as Vulnerable C2a(i).

This species is currently known from scattered disjunct subpopulations in high elevation aspen groves in the Sierra Nevada mountains in California, USA.

This species is currently known from four Quaking Aspen groves in the high Sierra Nevada of California. In total, aspen comprises only a small fraction (< 1%) of the Sierra Nevada landscape (Shepperd et al. 2006), and many of these stands are not habitat ideal for mushroom growth (i.e. exceptionally dry or rocky habitat). However, this habitat has been poorly surveyed for fungi.

Leccinum californicum was first collected in 1969, with a subsequent collection in 1971, and was not collected again until 2018. There was an unsubstantiated report from the type location in 2012. There were a few iNaturalist observations posted in 2020 which appear to be this species; spanning several months of fruiting in the same aspen grove (D. Morton pers. comm.) plus two additional observations from Lake Tahoe Basin posted in 2023 and 2024 (Mycoportal 2024, iNaturalist 2024). Due to the infrequent and sporadic reports, it is difficult to estimate its full population size, distribution, or population trends. Given the relatively small amount of suitable habitat and infrequent number of reports, it can be assumed that the species is rare to uncommon. Conservatively, it is estimated that there are no more than 500 additional appropriate sites for this species each with 10 to 20 mature individuals (Dahlberg and Mueller 2011) giving an estimated populations size of 5,000-10,000 occurring in these small, scattered subpopulations. Aspen groves in the Sierra Nevada are in decline (Rogers et al. 2007) and it is inferred that L. californicum populations are being negatively too.

This is an ectomycorrhizal species. Fruiting is solitary or scattered in soil and duff under Quaking Aspen (Populus tremuloides) at higher elevations. Fruiting occurs in summer and early fall.

There is a decline of aspen groves in the Sierra Nevada, due in part to conifer encroachment, fire suppression and cattle grazing (Rogers et al. 2007).

This species is edible (based on the 2012 reported find of this species); however, based on current knowledge on rarity, it should not be collected for food.

This species was included in A Field Guide to the Rare Fungi of California’s National Forests (Siegel et al. 2019), and was recommended for the Forest Service sensitive species list. Although aspen restoration projects are ongoing, effort should be made to cause minimal damage to the duff and understorey.

Targeted surveys of aspen groves in the Sierra Nevada and southern Cascade Range in California are needed, as is modern taxonomic work on California Leccinum.