Definition from the Australia Floral Art Association manual 2006.
“Decorative or topiary “trees” can be made in many styles, shapes and sizes from miniature to large scale, formal or informal. A sphere or cone of floral foam or wire netting filled with moss is suspended on a stem of natural or processed wood securely fixed into a container. The tree may have more than one stem and top, the decorative top comprising mixed types of plant material or only one. It is essential that the overall design is well balanced both visually and actually and the proportions of the three major components (container, stem, top) are pleasing. Plant material may be arranged in the container but should not be wider than the top.”