ASK MONTY...

Many years ago I planted a 30cm high conifer (left) 1.5m from our detached house. It is now 6m tall – are the roots a threat to the building?

John Mullin, Glasgow

A general rule of thumb in tree planting is to plant it the ultimate height of the tree away from the house – so a minimum of 6m in your case. If the foundations are good and the soil welldrained, you should be fine.

However, if the house has poor foundations on clay soil (as is the case on many Victorian inner city streets), then invasive roots could cause cracks. If you are worried, take it down and next time, plant further away!

l have lost most of my

Buxus to box tree caterpillars

(right). I don’t like using pesticides, but I only have three bushes left and I am picking the caterpillars off by hand.

Linda Worby, Clacton-on-sea

Sprays do not work. Pick them off or, even better, catch the parent moths at night before they lay their eggs. The prognosis is not good, I’m afraid.

I accidentally splashed weedkiller on the roots of my privet hedge, resulting in a ‘dead zone’. What can I do?

Peter Reed, Grimsby

Your best bet is to dig out the roots of the affected area, add in some compost and re-plant with healthy young bushes. They will soon refill the hedge.

Write to Monty Don at Weekend, Daily Mail, 2 Derry Street, London W8 5TT or email monty.don@dailymail.co.uk. Please include your full name and address. We regret Monty can’t reply to letters personally.