nsw, Australia

I live in Sydney Australia. I have just dug up 3 very old azaleas and a large clump of agapanthas. They were in a very confined position with a retaining wall behind them and a lawn in front. Around the roots and to a depth of about 3 inches is lots of white powdery stuff which looks a bit like ash.I would like to redo this bed and enlarge it and plant with new shrubs. Should I treat the soil before planting and how long should I leave it?.

• 6 May, 2009