Fertilization effects on mycorrhizal formation by Tricholoma virgatum with three pine species were studied. Inoculum was mixed into a 1 peat: 1 vermiculite media (1:9, v/v), prior to seeding in 160-cm3 “Leach Containers”. Four nutritional regimens were used: Full-strength Ingestad solution with 10% P, 10% Ingestad solution, modified-exponential Ingestad, and a slow-release fertilizer (Sierra TM, 17N-6P-1OK). Seedlings were harvested at 3, 4, and 5 months after sowing. Tricholoma inoculation resulted in 11% of the short roots of all species forming ectomycorrhizae (ECM) and 40% of the seedlings being colonized. P. sylvestris and P. nigra had significantly more ECM than did P. ponderosa, The number of ECM increased from the 3rd to the 4th month, but no increase occurred after the 4th month. Treatment with full-strength Ingestad/10% P yielded the largest seedlings and the least ECM, while exponential and 10% Ingestad produced smaller seedlings with the most ECM. The slow-release fertilizer treatment resulted in trees with intermediate growth and ECM formation. No differences in growth were found between inoculated and uninoculated trees.