Systems for production of out-of-season Protea cut flowers
The profitability of Protea cut flower production is in part determined by the extent to which flowering time coincides with market windows realising superior prices. In the Southern hemisphere the majority of commercially produced Protea cultivars, such as 'Brenda' and 'Susara', flower during late summer to autumn and may extend into winter which coincides with the lowest financial returns of the European spring and summer markets. Most Protea cultivars initiate inflorescences almost exclusively on a spring flush that develops terminally on an over-wintering shoot. However, cultivars such as 'Sylvia' and 'Cardinal' may initiate inflorescences on any flush, provided a sufficient number of subtending flushes are present. Other cultivars, such as 'Pink Ice', fall between these extremes and are able to initiate inflorescences on an autumn flush in addition to the preferred spring flush. All successful production systems that have evolved to manipulate the natural flowering times of Protea cultivars have in common a winter pruning of plants to synchronise shoot growth. In South Africa, at the onset of autumn, plants subjected to pruning during the previous winter usually consist of three flushes with the ensuing autumn flush having a higher propensity to initiate an inflorescence than the preceding summer formed flushes. In the case of 'Sylvia' and 'Cardinal', flowering is then concentrated between October to December. Flush extension and inflorescence initiation in 'Carnival' can be assisted by treating terminal buds on three-flush shoots with 500 mg L-1 benzyladenine (BA) in autumn. Flowering of these BA treated shoots is then typically advanced by three months to fall between November and January.