At its best:
Mar, Apr, May
Drill drainage holes in the container if necessary, and line it with plastic from an old compost bag, to stop the compost drying out. Cut the bag to size and pierce holes in the base.
Fill the window box two-thirds with compost.
Plant the daffodils in the centre, towards the back of the container, then book-end them with the primulas. Plant the daisies and the heather at the front. Add more compost around the plants and water thoroughly.