Never bring diseased or pest-ridden plants into your garden, because the problems may spread and become very difficult to control. Carefully inspect plants before buying them, and be wary of gifts of surplus plants from friends' and neighbours' gardens too.

If you're a vegetable grower, be on the lookout for clubroot on plants from the cabbage (Cruciferae) family. Once this root disease gets into the soil you will not be able to get rid of it. Nor will you be able to grow cruciferous vegetables or flowering plants successfully.