Notes From a Sceptical Gardener - More expert advice from the Telegraph columnist

What is the best way to kill weeds in paving? How scared should we really be of Japanese knotweed? And what is a weed anyway?Biologist Ken Thompson set out to write a different kind of gardening column, one that tackles what he calls ''the grit in the gardening oyster''. In this new collection he takes a look at some of the questions faced by gardeners everywhere in a bid to sort the truth from the wishful thinking.Why are the beaks of British great tits getting longer? Which common garden insect owns a set of metal-tipped running spikes? Why might growing orange petunias land you in hot water? Are foxes getting bigger? How do you stop the needles falling off your Christmas tree?This expert''s miscellany of (mostly) scientifically-tested garden lore will make you look at your garden through fresh eyes.