IT IS ESSENTIAL that containers have adequate drainage otherwise the planting medium will get waterlogged and the plant roots rot. Make sure the containers have at least one large central drainage hole if not more, and place a layer of crocks (broken pieces of clay flowerpot) on the bottom of the container before filling it with compost Containers should also be raised from the ground on bricks or flat containers such stones so any exces water can drain out.
A layer of well-washed pea gravel can b( used instead of crocks for more permanent displays, such as those involving shrubs or small trees.
In many respects, small containers are more difficult to place. Several small containers scattered about do not necessarily make a bold impact and can look fussy. Furthermore, a group of small containers can also be more difficult to maintain. However, they do come into their own when placed around the edges of larger containers to soften their outlines.
Try to create different levels when you group containers and arrange them in a tiered manner. Not only is this visually more exciting than a uniform row of pots, but each planting will be displayed to best effect and create a terrace-like cascade of foliage. Do not mix too many different types of containers in one group. Either choose containers of a similar style, or stick to one type of material, such as terracotta.