Abstract Glass-fronted boxes inserted in paths adjacent to nursery seedbeds were used to study root development of seedling white spruce, Picea glauca (Moench) Voss, during the third growing season. Total oven-dry weight increased about fourfold, tending to be linear through the season, but almost 20 percent occurred after September. The top-root ratio more than doubled, increasing very rapidly during the early part in the season to a maximum of 3.9:1, then decreasing. Visible root and top growth began almost concurrently with a flush of root activity in the spring at the time of a bud swelling; and a secondary flush in early fall. The rate of root elongation, as measured on individual roots against the glass surface, had a spring maximum, a severe depression during shoot growth, a more moderate level through the summer, and a slow decrease in the fall.