PLANTING STOCK QUALITY AND GRADING

The act of grading is, supposedly, an attempt to separate plants into classes of different degrees of usefulness in forestation. Ideally, grading of nursery stock for planting should therefore be based on rotation-long performance potential at the time of out-planting. In practice, grading in advance of outplanting, even if perfect, may be vitiated by subsequent changes. Also, the central problem is to relate securely the criteria used in grading to outplant performance. Morphological criteria have hitherto served only tolerably well, and even with conventional spring- and autumn-lifted stock planted without delay, morphology has often belied field performance. Physiological factors, especially those influencing root regeneration, winter vigour or hardiness, dormancy, and disease resistance, are becoming increasingly important with the use of unconventional lifting, outplanting, and storage practices that disrupt growth rhythms or reduce vitality. Monitoring and characterization of representative planting stock from seed through to established reference plantations are needed to generate the data on which rational grading practices can be based. © 1979.