When camellias are infected by Ciborinia camelliae, hard, black resting structures called sclerotia develop within the base of the decaying petals. These survive as the rest of the fallen flower rots down, and remain dormant in the soil during winter. The sclerotia germinate, producing small, brown, cup-shaped reproductive structures called apothecia. These can sometimes be found on the soil surface below an affected plant, but can be very difficult to spot amongst the old flower and leaf debris.
Huge numbers of spores are released from the surfaces of the apothecia and are carried upwards in air currents to reach camellia flowers. These spores require the petals to be wet to infect, so infections are more common in wet weather.
Sclerotia of Ciborinia camelliae can survive for up to five years in the soil. Not all of them will germinate in the first year, and an individual sclerotium can germinate for more than one year. The spores may travel up to 20km (12 miles) on the wind. Apart from these wind-blown spores, the fungus can be spread over long distances in soil contaminated with the sclerotia, for example on muddy boots or car tyres.