Before planting anything permanently, take time to arrange your plants on top of the soil and step back to look at the container from all angles. This dry run is one of the most important steps in creating a container that looks balanced, full, and intentional rather than crowded or awkward.
A helpful design framework for container plantings is the thriller, filler, spiller approach. While it sounds simple, a few guiding principles will help you use this method successfully.
Start with the Thriller
The thriller is the plant that provides height and visual drama. It draws the eye upward and gives the container a clear focal point. In round pots meant to be viewed from all sides, place the thriller in the center. In containers viewed mainly from one side—such as pots against a wall or railing—position the thriller toward the back.
Good thrillers have strong vertical form or bold foliage, such as ornamental grasses, cannas, coleus, salvias, or small shrubs. When choosing a thriller, consider its mature height and width. A plant that is too tall can look top‑heavy, while one that is too small may disappear once fillers grow in.
A useful rule of thumb is that the thriller should be roughly one and a half to two times the height of the container.
Build the Body with Fillers
Fillers create fullness and connect the thriller to the edges of the pot. These plants typically have mounded or upright forms and medium height. Arrange fillers around the thriller, spacing them evenly so the container looks balanced as the plants mature.
Choose fillers with contrasting leaf shapes, colors, or textures to keep the planting visually interesting. For example, pairing fine‑textured foliage with broader leaves adds depth and richness. Fillers should complement—not compete with—the thriller, so avoid using too many bold plants at once.
Remember to leave enough room for growth. Containers fill in faster than many gardeners expect, and overcrowding can limit airflow and reduce flowering later in the season.
Finish with Spillers
Spillers soften the edges of the container and visually tie it to the surrounding space. These trailing plants should be placed near the rim of the pot, where they can cascade naturally over the sides.
Position spillers so they don’t overwhelm the container or hide the other plants. In most pots, two to four spillers are plenty. Good choices include sweet potato vine, creeping Jenny, calibrachoa, bacopa, or trailing petunias.
Think about viewing angles when placing spillers. If a container sits at an entryway or along a path, place spillers where they will be most visible and won’t interfere with foot traffic.
Step Back and Adjust
Once all plants are positioned, step back and look at the container from several directions. Check that the planting feels balanced and that no single side looks heavy or sparse. This is the moment to make adjustments—turning a plant, swapping positions, or removing one if the container feels crowded.
Taking time to arrange before planting ensures that when everything goes into the soil, your container will grow into a cohesive, polished display that looks good from planting day through the height of the season.
North Shore Plant Club
