All containers need to be given adequate drain, but you must take extra care with winter containers to avoid damaging the bulbs. Choose a soil based potting compost or soil mix or use a peat based compost and add extra grit, in the ratio of approximately three parts compost to one part grit, in the ratio of approximately three parts compost to one part grit.
Before planting you need to place a layer of broken pots or polystyrene or Styrofoam at the base of the container, which will help to give extra drainage in periods of continued wet weather.
The drainage layer will also help to prevent the roots of the plants from blocking the drainage holes, which are sometimes too small in relation to the size of the pot.
Wooden containers will often rot. To slow down the process, add a lining of plastic sheeting, which will retain the moisture in the compost and keep the dry wood on the inside. Make holes in the base of the plastic to match the holes in the container base.
The lining also helps minimize moisture loss through evaporation in late spring when the container may be in danger of drying out. Position the shrub or the cornus so that it sits just below the rim.
Plant the daffodil bulbs, base down, nose up, close to the edge of the barrel, so that the tips of the bulbs will be at an historical depth below so level of three times their own height, allowing for a 5cm or 2in gap at the top of the container.
Add more compost, and then plant the skimmias and heucheras on opposite sides of the barrel. Fill in the gaps with more compost to within 2.5cm or 1in of the rim. Plant the pansies around the edge. Water it well.