Pieces of polystyrene boxes will also do. This allows for better drainage and reduces rotting at the base of a wooden container. Only choose strong healthy plants that are bushy and well branched. Make sure the rootball is moist before planting. Leave a space at the top of the container for watering.
Saucers are useful when watering and prevent staining surfaces.
However, don't leave plants sitting in water for too long or the roots will rot. Wait until after the risk of frost has passed before placing bedding plants outside. As a general rule, most plants appreciate a sheltered position with plenty of light. If you decide to use a variety of species in one pot, choose themes using similar leaf shapes, shades of foliage and flowers. In winter, be sure to choose hardy plants, because on bad days their roots will be completely frozen.