Influence of Growth Medium pH on the Growth of Container-grown Fraser Fir Seedlings

Abstract

Seedlings of Fraser fir (Abies fraseri (Pursh) Poir.) were grown in sphagnum peat amended with 0 to 8 kg dolomitic limestone/m3 (0 to 13.5 lb/yd3). Initial pH ranged from 3.9 to 6.7. Best growth (21.2 cm (8.3 in) mean height at 19 months) was achieved with 1 and 2 kg/m3 (1.7 and 3.4 lb/yd3), with initial mean pH 4.2 and 4.5. Seedlings grown in media amended with 4 and 8 kg/m3 (6.7 and 13.5 lb/yd3) grew more slowly (17.4 (6.9 in) and 9.5 cm (3.7 in) in 19 months), and many were chlorotic, with poorly formed, blackened roots. At the conclusion of the first growth cycle (10 months), the slowest growth occurred in the most heavily limed peat (8 kg/m3 (13.5 lb/yd3), initial pH 6.8). Slower growth at 4 kg/m3 (6.7 lb/yd3, initial pH 5.0) became evident only after three growth cycles. Seedlings grew best within a fairly narrow range of pH (4.2 to 4.5), which is considerably more acidic than is generally recommended for conifers.