What is the difference between proportion and scale in floristry?

Proportion and scale are often confused, but each has a precise and distinct meaning. Proportion deals with amounts - the relationship of the parts of a design to each other and to the space it occupies. A general guide is that plant material should be one and a half to two times the height or width of the container, though there are no absolute rules on proportion. Scale refers to the relative sizes of individual materials within an arrangement. Using only two flowers of vastly different sizes without transitional material between them will not produce a pleasing design - grading the sizes of materials, and incorporating transitional flowers to link size extremes, helps achieve the desired harmony. The simplest way to remember the distinction: proportion deals with amounts; scale deals with sizes. Sources: Pampling (100, 105, 220).