 "Suillus lakei" forms ectomycorrhizae with Douglas fir ("Pseudotsuga menziesii"), and its distribution coincides with this tree.It is one of the most common bolete species found in northwestern Montana and Idaho.In a study of host specificity in pure culture in the laboratory, "S. lakei" failed to form healthy ectomycorrhizas with "Eucalyptus" roots—the hyphae were covered in mucilage-like deposits and appeared to be collapsed.