Copper Root Pruning and Container Cavity Size Influence Longleaf Pine Growth through Five Growing Seasons

Abstract

Restoring longleaf pine (Pinus palustris Mill.) over much of its historic range requires artificial regeneration, and most often, container-grown seedlings are used. However, type and size of container can influence field performance. In this study, longleaf pine seedlings were grown in Beaver Plastics Styroblocks either without a copper treatment (Superblock) or with a copper oxychloride coating (Copperblock) and with three sizes of cavities that were 60, 108, and 164 ml. Seedlings from the six container types (two types of Styroblocks with three cavity sizes) were planted in central Louisiana in a 2 by 3 randomized complete block factorial design. Emergence from the grass stage was quickest for seedlings outplanted from either Copperblocks or large cavities (164 ml), but 99.3% of all seedlings had emerged after five growing seasons. Five-year-old trees outplanted from Copperblocks were significantly taller and had greater volume index (VI = [groundline diameter]2 × [total height]) than trees outplanted from Superblocks (2.0 m tall and 114 VI versus 1.7 m tall and 87 VI). Trees outplanted from small cavities (60 ml) were shorter and had a smaller VI (1.5 m tall and 73 VI) than trees outplanted from the other two cavity sizes (average of 2.0 m tall and 114 VI).