You need to pick off and destroy (not compost) all the affected leaves and then feed your plant with bonemeal or phosphorus which will promote strong roots and potassium which encourages strong growth. This will help make a strong plant that can fight off pests and diseases.
Keep nitrogen to a minimum as this makes for soft, sappy growth which is more susceptible to pests and diseases. Tomato fertiliser would work well if you can't get the individual components.
Vendée - 20kms from Atlantic coast.
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It looks like it may be rust. There's some info here about how and why it occurs - https://www.rhs.org.uk/advice/profile?pid=756 and how to treat it.
You need to pick off and destroy (not compost) all the affected leaves and then feed your plant with bonemeal or phosphorus which will promote strong roots and potassium which encourages strong growth. This will help make a strong plant that can fight off pests and diseases.
Keep nitrogen to a minimum as this makes for soft, sappy growth which is more susceptible to pests and diseases. Tomato fertiliser would work well if you can't get the individual components.
Help! some of the leaves of my red hot pokers are covered in black. What is it and what should I do?