PURPOSE: To provide a light-weight vessel for restricting the root area of a plant, made of a foamed synthetic resin containing a water-insoluble copper compound, effective for preventing the intrusion of root hair between expanded beads and capable of restricting the root area without inhibiting the growth of the plant.

CONSTITUTION: A pot tray, etc., of a root area restriction vessel is formed with a foamed synthetic resin containing a water-insoluble copper compound such as cupric hydroxide. The transplantation of a seedling can be smoothly performed without causing the catch of the root hair on the inner wall of the pot tray.