The effects of amendation of two mine spoils (oil sands tailings and a subalpine coal mine spoil) on the development of vesicular–arbuscular (VA) mycorrhizae with Agropyron trachycaulum were examined over 4 years. Each spoil was either amended with peat, fertilizer, or sewage sludge or left unamended. Plants were sampled in late August of the second and fourth growing season and the level of infection expressed as length of mycorrhizal root per 10 cm3 of spoil. Plants on the peat-amended oil sands spoil, as compared with the other treatments, had the highest rates of infection. Infection levels increased in the fertilized plots over the 4 years. Mycorrhizae were not detected in the sewage-amended plots until the 4th year. Infection levels from the amended subalpine spoil did not change significantly between the 2nd and 4th year. Mycorrhizal root lengths were highest in the peat-amended spoil as compared with the control and sewage-treated plots. Rates of infection in the fertilized spoil were not significantly different from the other treatments. The initial application of an amendment to a mine spoil may have significant long-term effects on the development of VA mycorrhizae and the success of a revegetation program. Changes in the mycorrhizal status of plants on these habitats may occur only slowly with time.