Efficacy of Flurprimidol and Peat Alternatives on Growth Control of Potted Camellias

Potted camellias tend to grow more than desired and sometimes in association with poor flowering. Growth regulators of the triazole group have been successfully applied to overcome these issues in the past, however, recent restrictions on the group indicate that new growth retardants must be considered and tested. Concurrent with this change is the need to reduce the horticultural use of peat (potting mixture), a world resource being quickly depleted. Given these two aims, we evaluated the efficacy of flurprimidol, in combination with three peat alternatives (reused nutshells, rice husk, and coconut fibres), to control the growth of four Camellia japonica cultivars. Results showed that all considered peat alternatives, especially rice husk, were suitable as partial substitutes. Results also showed that at low concentrations, flurprimidol controlled height (12-13% reduction) and enhanced flowering (three flowers per plant versus two). However, we suggest that the growth regulator input be adjusted based on the cultivar and substrate type, as the three factors interact strongly.