Effect of container type and seedling size on survival and early height growth of Pinus palustris seedlings in Alabama, U.S.A.

Three hardwall container types, one styroblock® container type, and two mesh-covered plugs were used to grow longleaf pine (Pinus palustris Mill.) seedlings at a nursery in Louisiana. In 2001, these container types, along with bare-root seedlings (from a different seed source), were outplanted on two old-field sites and two cutover sites. There were significant site by treatment interactions. Second-year survival was higher on cutover sites than on old-field sites. Root-collar diameter of container-grown stock was positively related to root growth potential (RGP) and height after two growing seasons. Container-grown stock with the lowest RGP exhibited the lowest overall seedling survival. On three sites, field performance of seedlings grown in mesh-covered plugs was less than seedlings grown in other types of containers. For styroblock® trays, treating cell walls with copper increased RGP but did not affect field performance. Increasing the spacing between container cells increased diameter and height after two growing seasons. A root bound index (RBI) was developed and was calculated for each container seedling by dividing root-collar diameter by the diameter of the container cell. Survival was low when RBI was greater than 27%. Although large-diameter bare-root stock can be advantageous as far as survival and growth is concerned, the same may not be true for containers. Some 7-month old container seedlings might become too large for some container types.