Camellias are one of the few winter flowering shrubs that will respond to pruning if necessary. It is important to realise that the flower buds for the Camellia are formed in early summer, ready to flower in late autumn or winter a few months hence. Any pruning carried out should be done right after flowering, in order to allow the shrub enough time to produce new shoots and flower buds.
Late pruning will inevitably result in a winter season with few or even no flowers. Late pruning of Camellias and other winter flowering shubs is one of the main causes poor or no flowers.
The shrub needs time through the spring and summer growing season to firstly produce new shoots and then produce the flower buds on those shoots ready for winter flowering. Flowers don't simply happen. They are a result of flower buds sometimes produced several months before actual flowering.