By Clarkj
West Sussex,
United Kingdom 
My questions concern my Camelias and a osteospermum. As you will see from the attached photos my camelia's leaves have large areas of yellow. My osteospermum which has been in the border for 2 seasons has always produced an amazing amount of flowers. But this year the plant has developed what looks like a white mould! Can you help me with both problems please. Many thanks
On plant
Thanks for your response. Regarding the camillia - it has been in the border (with echinacea soil added) for 2 years and it is only this summer that the leaves have gone blotchy. They were originally a lovely glossy green all over. How do I rid the ost
30 Oct, 2011
Answers
The yellowing of your camellia leaves could be a symptom of Lime Chlorosis. Too much lime in your soil is blocking the uptake of iron to your Camellia plant which in turn is causing the leaves to yellow. Short term you will need to feed your plant with an ericacious/acid fertiliser and you will also need to apply a dressing of ferrous sulphate fertiliser to the soil to replenish the iron.
30 Oct, 2011
It looks suspiciously, though not entirely, like virus damage. I hope that it isn't, since there isn't any cure if it is. If just a few branches are affected, you might try cutting off those branches close to their origin, and sterilizing the shears or saw with bleach solution between cuts.
31 Oct, 2011
Thanks you all so much. I'm new to this site and so glad I joined.
31 Oct, 2011
Your osteospermum has mildew. The camelia is more interesting. If the whole leaf has turned yellow, I would have said that it had become chlorated, lacking magnesium or iron, often because the soil is alkaline. Have the leaves always been bi-colour, or is this a recent occurance? It could be an unstable variety and a genetic fault.
30 Oct, 2011