Évaluation de trois contenants pour la production de plants d'espèces feuillues de fortes dimensions

Abstract

Three types of containers of different volumes (Polymos 15, 700 cm3; Polymos 12, 1,000 cm3; Whitcomb®, 3,500 cm3) were tested to produce 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 to assess containers after two growing seasons in an unheated plastic shelter. The mean height of seedlings increased with the volume of the containers. The total dry mass of seedlings at 55 cm in height was more important in the larger container; the total root mass and the proportion of secondary roots were higher in the container of greater volume. For the two species of oak, the 3,500 cm3 container produced seedlings with a taproot showing a number of deviations when touching the bottom of the container. White ash, a species with a fibrous root system, showed a higher deviation index in the smaller containers. The openings on the sides of the square-shaped Whitcomb® containers were effective for the air-pruning of secondary lateral roots of species with a taproot and their volume allowed for an important root mass. However, the flat bottom with openings at each of the four corners did not prevent deviation of the primary root. The use of a bottomless square-shaped container with a volume greater than 1,000 cm3 and with adequate lateral openings would optimize the production of large seedlings of hardwood species with taproot. Key words: large containerized seedlings, root development, root deviation, Quercus sp., Fraxinus sp.