Join the RHS today and support our charity
Free personalised gardening advice
RHS members get reduced ticket prices
RHS members get free access to RHS Gardens
Reduced prices on RHS Garden courses and workshops
020 3176 5800
Mon – Fri | 9am – 5pm
Help us achieve our goals
Make a donation
I have forgotten my password
Keep me signed in
Register for free to receive our newsletters, add comments to blogs/articles and to save content.
See what events are on near you and browse your bookmarked pages.
Camellia flower blight is a fungal disease of camellias, attacking the flowers and causing them to rot.
Camellia flower blight is a disease caused by the fungus Ciborinia camelliae. The fungus is capable of overwintering in the soil in the vicinity of affected plants.
It was first described in Japan in 1919 and has since spread to the USA, New Zealand and parts of mainland Europe. It was first found in the UK in 1999 and is now present quite widely through southern England, including at RHS Garden Wisley.
The disease is restricted to camellia, and affects no part of the plant other than the flowers. It is only found, therefore, while the plants are in flower.
You may see the following symptoms:
Flower blight can be distinguished from grey mould by removing the calyx from the base of the flower. The flower blight fungus produces a characteristic white or greyish ring of fungal mycelium around the base of the petals. Occasionally, oily black droplets (one of the spore stages of the fungus) are also found towards the bases of the petals. By contrast, grey mould will often produce large numbers of powdery grey spores over the affected material.
Cleaning up fallen flowers will help reduce infection in following years.
Putting down a deep mulch to bury the sclerotia might help, but the apothecia (see Biology, below) are produced on stalks that can grow up to 10cm (4in) in length. The mulch may have to be too deep to be practical.
Fungicide spraying is not a realistic option and there are no fungicides labelled for home use; nor are there any products available for soil treatment.
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 as the plant comes into flower the following year, 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 them, 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.
Brown leaves on woody plantsCamelliaCamellia problems: frequently asked questionsCamellia gallCamellia leaf blightCamellia yellow mottle virusDisposing of diseased materialFrost damageRHS Rhododendron, camellia and magnolia groupScale insectsSooty moulds
the RHS today and get 12 months for the price of 9
RHS members can get exclusive individual advice from the RHS Gardening Advice team.
Register for the site or sign in to share your experiences on this topic and seek advice from our community of gardeners.
We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.
Join the RHS today and get 12 months for the price of 9