In the gardening world few plants are as consistently fragrant as those we describe as herbs. And few sensations stir the memory as forcefully as that of scent. How many of us, at the first hint of the clove-like bouquet of basil or caught in the lee of a gust of air heavy with the perfume of lavender, can prevent long-forgotten images crowding into the mind. And who would want to. Time and again gardens are planted, food is prepared and perfume is rubbed on to skin as a deliberate aromatic evocation of good times remembered.