EVALUATION OF 3 CONTAINERS FOR THE PRODUC TION OF LARGE HARDWOOD SEEDLINGS

Three types of containers of different volumes (Polymos 15, 700 cm(3); Polymos 12, 1,000 cm(3); Whitcomb(R), 3,500 cm(3)) were tested to pro duce large hardwood seedlings. Studies of growth and root development of three species, white ash (Fraxinus americana L.), bur oak (Quercus macrocarpa Michx.) and northern red oak (Quercus rubra L.) were used t o assess containers after two growing seasons in an unheated plastic s helter. The mean height of seedlings increased with the volume of the containers. The total dry mass of seedlings at 55 cm in height was mor e important in the larger container; the total root mass and the propo rtion of secondary roots were higher in the container of greater volum e. For the two species of oak, the 3,500 cm(3) container produced seed lings with a taproot showing a number of deviations when touching the bottom of the container. White ash, a species with a fibrous root syst em, showed a higher deviation index in the smaller containers. The ope nings on the sides of the square-shaped Whitcomb(R) containers were ef fective for the air-pruning of secondary lateral roots of species with a taproot and their volume allowed for an important root mass. Howeve r, the flat bottom with openings at each of the four corners did not p revent deviation of the primary root. The use of a bottomless square-s haped container with a volume greater than 1,000 cm(3) and with adequa te lateral openings would optimize the production of large seedlings o f hardwood species with taproot.