A Re-evaluation of Wakeley's “Critical Tests” of Morphological Grades of Southern Pine Nursery Stock

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Abstract
Data presented by Wakeley on field performance of subgrades of slash pine (Pinus elliottii Engelm. var. elliottii) and longleaf pine (Pinus palustris Mill.) seedlings were reexamined in the light of more recent studies indicating that morphological grades for southern pines are reliable predictors of field performance. It was learned that all longleaf pine subgrades tested by Wakeley are now considered as culls which may explain why he did not report the height growth after planting for this species. To produce seedlings with larger root-collars which emerge from the “grass” stage more quickly than seedlings tested by Wakeley, nursery managers in the southern United States are currently growing longleaf pine at much lower seedbed densities than recommended by Wakeley. The reexamination of Wakeley's data for slash pine seedlings found that instead of being inferior to smaller seedlings, the overall survival of grade 1 seedlings (root-collar diameter > 4,7 mm) was equal to grade 2 seedlings (root collar diameter 3,2 mm to 4,7 mm) and was better than cull seedlings (root collar diameter < 3,2 mm). Initial growth of grade 1 seedlings was better than for either grade 2 or grade 3 seedlings. Differences in field performance between beds were great and, if measured, might have been explained by differences in seedbed density and/or shoot/root ratios. As Wakeley indicated, the differences in field performance of seedlings from different beds but with similar morphological characteristics can result from differences in physiology due to different cultural practices, soils, or seed sources.

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