Keeping your window boxes disease free
However, certain diseases, such as tomato and potato blight, contaminate the soil so much that it is best to throw away any compost that plants affected with these problems have grown in.
Nip disease in the bud
Always remove dead flowers and leaves, and any other unhealthy plant material as soon as you spot them.
Clean the area around your, window boxes regularly, and never compost anything that you know to be infected.
Like people, plants under stress are more vulnerable to disease than those bursting with vitality.
Keep plants well fed to give them the best chance of survival. Fertilisers that are high in phosphates and potash produce strong root systems and tough, disease-resistant growth, while those with high levels of nitrogen can encourage lax, soft growth, which is easily invaded by diseases.
Under watering also puts plants under stress, making them vulnerable to disease, while plants grown in waterlogged window boxes will have poor root health and weak, sickly growth.