Why are my onions, runner beans and lupins showing poor growth? 

Garden Q&A: Our columnist Peter Dowdall has the answers to your questions

A row of onions ready for harvest. Picture: iStock

Question: The past two years my onions, runner beans and lupins have shown very poor growth. The roots appear to have been nibbled and stunted. Could you advise me of the likely cause and possible cure? I am a senior citizen and the garden is my only outlet these days.

Answer: I cannot accurately say what is causing the problems without seeing them, however, the importance of crop rotation cannot be overstated. Growing any crop such as onions and beans on the same patch of ground each year can lead to a build-up of a pest or disease and thus the problem can get much worse. Moving your crops to different areas each year will help to counteract that. It may well be one or more fungal infections causing the root problems and so a drench with a solution of copper sulphate and water will help. This is an organic broad-spectrum fungicide that should only be used once a year. Finally, adding organic matter to the soil will help to improve structure, texture and nutrient content and this can only help all of the plants. Improving the texture will increase pore spaces in the soil which are essential for good root development.  Finally, adding organic matter to the soil will help to improve structure, texture and nutrient content and this can only help all of the plants. Improving the texture will increase pore spaces in the soil which are essential for good root development.