At its best:
Mar, Apr, May, Jun
Place a layer of crocks in the base of the window box to help with drainage.
Fill the window box two-thirds full with compost and tap it down to get rid of any air pockets in the corners.
Plant the primula and ranunculus in the middle, and violas in the gaps, for an even mix of colour. Water well, allow to drain and move the window box to its final position.