To create pleasing container arrangements, floral designers use what is called the thriller-filler-spiller technique. In selecting plants to be combined in a container or hanging basket, florists look for plants that will fill each role:
Thriller. Usually a tall plant that gives height to the arrangement, thillers create a central focal point that captures attention. Thrillers are placed in the center of the container and the rest of the arrangement is literally built around them. Tall grassy plants like Cordyline, spiky flowers like Digitalis and plants with unusually shaped or colored leaves like Coleus make excellent thrillers.
When selecting a thriller for your container arrangement, consider color as well as height and shape. You can use a thriller to tie a container arrangement together by repeating colors from the thriller in your filler and spiller selections. Or you can choose a thriller in a bold, contrasting color to create maximum impact.
Filler. Filler plants are placed in a circle around the thriller. Their purpose is to “fill in” the arrangement by creating a pleasing mass of form and color. Filler plants carry the color theme of the arrangement and are generally selected for their showy blooms and compact growing habit which concentrates a profusion of flowers in a small space. Good filler choices include colorful Petunias, delicately flowered Begonia Fibrous (Begonia) and Bellis, also known as English Daisy.Spiller. Spillers are trailing plants that spill over the sides of the container, providing a visual aid that connects planters to the ground or emphasizes the airiness of hanging baskets. English Ivy (Hedera) is a perennially popular spiller; it’s shiny green leaves providing a lovely counterpoint to any plant grouping. For a colorful spiller, try Calibrachoa which blooms in a profusion of bell-shaped flowers all summer long. Ivy Geranium (Pelargonium) adds both color and leaf interest to container plantings.