Blueberries need to pass acid test

How do I keep the compost acidic for my pot-grown blueberries? Dennis, Worthing, Sussex

DAVID: Blueberries prefer to grow in acidic soil with a ph of 5.5 or lower. Planting them in ericaceous (acidic) compost will give them a good start.

Keep soil acidic by giving plants a regular source of iron in their water. Buy sachets of sequestrene of iron from the garden centre, and add it to your watering can.