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