Peter Dowdall: When to cut back hydrangeas and how to prune ornamental grasses

'Both are signs in February that the switch is going off within us, and we need to get outside to the garden once more'

Purple, blue and pink Hydrangea flowers (Hydrangea macrophylla). File pictures 

Two of the questions I am most often asked at this time of year are when to cut back hydrangeas and how to prune ornamental grasses. Both are signs that the switch is going off within us, and we need to get outside to the garden once more.

February sits in that almost-spring space, light stretching longer each evening, buds beginning to swell, soil workable when it's dry, but still cold.