What Are Fillers in a Planter?

Fillers Explained

• When designing a container planting, some gardeners use filler plants in combination with thrillers and "spillers." The thriller is the star of your planter and is typically a tall, upright plant with some exceptional quality, such as bright flowers or foliage, or an interesting shape. The thriller should draw your eye. Spillers are plants that spill over to soften the edges of the container and accent the filler and thriller plants. Ground covers and vining plants work well as spillers. Fillers make the middle layer of your container and add complementary texture and color to the thriller plant. You can also use filler plants to add texture, color and substance around shrubs elsewhere in your landscape.

The Right Formula

• The key to a successful container planting is in knowing how many of each type of plant to include. A 12-inch diameter pot can usually fit about six plants: one thriller, two fillers and three spillers. In a larger, 18-inch pot, you’d still use one tall thriller plant, but add another filler and a spiller. Tall thriller plants go in the center of the pot because they’re the stars, and the smaller fillers go around the base of these; spillers are planted around the sides. Try to limit the variety to three or four plants to ensure that the result is a cohesive planter that works together, instead of a bunch of different plant species fighting for attention.

Shade-Loving Fillers

• If you’ve selected a thriller that does best in shaded conditions, you’ll need a filler plant with the same light requirements. Begonias are available in a variety of colors, and do best in partial shade, although they will also grow in bright, indirect sunlight. Begonias are typically hardy to U.S. Department of Agriculture plant hardiness zones 10 and 11. Another shade-loving option that thrives in partial to full shade is "Bellingrath Pink" coleus (Solenostemon scutellarioides "Bellingrath Pink"), which is hardy to USDA zones 10 and 11. This filler complements any thriller with its evergreen foliage in shades of pink and green. Common periwinkle (Vinca minor "Illumination") is an attractive filler that thrives in full shade, and is hardy in USDA plant hardiness zones 4 through 9.

Sun-Loving Fillers

• If you’ve selected a filler plant that loves sunshine, you have several filler options. For example, "Margarita" sweet potato vine (Ipomoea batatas "Margarita") boasts colorful burgundy foliage. This filler grows best in full sun to partial shade and is hardy to USDA plant hardiness zones 10 and 11. For an extra boost of color and texture, try Joseph’s coat (Alternathera ficoidea). Depending on the cultivar, this filler’s leaves are blotched with yellow, red, orange or purple. Joseph’s coat is also hardy to zones 10 and 11, and thrives in full sun to partial shade. Other colorful fillers for sunny locations include marguerite daisies (Argyranthemum frutescens "Madeira Primrose") and white petunias (Petunia Supertunia "Mini White"), both hardy to zones 10 and 11.