Reducing peat and growth regulator input in camellia pot cultivation

Regulating plant development plays an important part in Camellia japonica L. pot production. Cultivation usually occurs on peat-based substrate and growth control is performed with triazoles application. However, an increasing need for finding suitable peat alternatives and more effective protocols is rising. This study evaluated the effectiveness of three different dosages (50, 100, 200 mg l-1) and two application protocols (foliar spray, once or twice) of paclobutrazol on two C. japonica cultivars grown on eight different substrate mixtures. The substrates were composed by four peat substitutes (local green compost, pumice, composted coconut peat, and pine bark) mixed with the standard substrate at 30-40% by volume. Treated plants showed reduction in most of the growth-related parameters, enhancement of ornamental value and an overall plant health improvement. Basically, one application of paclobutrazol 50 mg l-1 was sufficiently active. Among substrates, pine bark appeared a suitable partial peat alternative. Considering their lower cost and effective performances, pumice and coconut peat resulted suitable alternatives too.