Planting flowers in containers is an easy and practical way to add a splash of color to your balcony, patio, or garden. But have you ever looked at your flower pots and found them a bit … boring? If that’s the case, it’s time to learn how to elevate your planters using thrillers, fillers, and spillers. This simple design recipe can transform any potted flower arrangement into an absolute showstopper.

In this guide, we’ll highlight how to create fantastic container arrangements every time. We’ll offer some of our favorite examples of thrillers, fillers, and spillers, and provide valuable tips on combining them for the best effect. 

What Is the Thriller/Filler/Spiller Rule?

The golden rule for creating the best container displays is using three different types of plants that play three different roles. Thrillers provide the focal point, fillers complement the thrillers while filling the space, and spillers tie everything together while tumbling over container edges.

The result is a three-tiered flower arrangement that looks full, lush, and visually engaging.

Thrillers

Thrillers are the centerpiece of your container display. They are the tallest plants in your arrangement and dictate the tone for the rest of your planting. Thrillers can be either vibrant, colorful flowers, foliage plants that provide structure and interest, or a mix of both.

Because thrillers are the stars of the show, always pick just one variety for your container, and plant it in an odd number — ideally one or three plants. Otherwise, you risk creating an unbalanced display.

Plant your thriller in the middle of your container if you’re looking at it from all sides, or at the back if you’re viewing it from the front.

Thrillers for full sun:

•  Canna lily
•  Aster
•  Allium
•  Verbena bonariensis
•  Gladioli
•  Agave
•  Dracaena
•  Dahlia
•  Salvia
•  Rudbeckia
•  Achillea (yarrow)
•  Eryngium
•  Echinacea
•  Nerine
•  Tall ornamental grasses: Stipa, Miscantus, Pennisetum

Thrillers for part shade:

•  Bromeliads
•  Cordyline
•  Astrantia
•  Polemonium
•  Fuchsia (cultivars: Beacon, Delta’s Sarah, Empress of Prussia, Genii, Garden News)

Fillers

Fillers play an essential role in creating continuity between the planting layers of your container. As the name suggests, they fill in the middle space, but without drawing attention from the thrillers. They are usually medium-sized plants with compact shapes and can be either flowering or foliage plants.

For best results, pick up to two different types of fillers and plant them in an odd number. Avoid choosing fillers that are more than half the size of your thrillers, otherwise they will overwhelm and undermine them.

Fillers for full sun:

•  Geranium (cultivars: Rozanne, Orion, Elizabeth Ann, Kashmir White)
•  Pelargonium
•  Petunia
•  Pentas
•  Agastache
•  Erigeron
•  Lavender
•  Aster
•  Osteospermum
•  Ageratum
•  Gazania
•  Gypsophila
•  Geum
•  Coreopsis
•  Scabious
•  Candytuft
•  Zinnia

Fillers for part shade:

•  Fuchsia (cultivars: Arauco, Alice Hoffman, Jack Stanway, Tom Thumb, Lady Thumb)
•  Impatiens
•  Pansy
•  Begonia
•  Alstibe
•  Dicentra
•  Heuchera
•  Coleus
•  Nepeta
•  Persian shield
•  Alchemilla mollis
•  Nemesia
•  Persicaria
•  Corydalis ‘Blue Heron’
•  Hosta
•  Ferns

Spillers

Spillers act as a visual anchor for the display, softening sharp contours as they spill over the edges of the pot. They also round up the theme of your floral arrangement by repeating the colors and shapes of the thrillers and fillers.

Choose one or two varieties of spillers and plant them on the edge of your pot. For a dramatic effect, you can also pick colors that form a bold contrast with the color of the container.

Spillers for full sun:

•  Pelargonium (ivy geranium)
•  Sedum
•  Nasturtium
•  Lobelia
•  Bacopa
•  Calibrachoa
•  Erigeron karvinskianus
•  Geranium ‘Pink Spice’
•  Sweet alyssum
•  Sweet potato vine
•  Herbs like thyme and oregano
•  Strawberries

Spillers for part shade:

•  Nasturtium
•  Muehlenbeckia
•  Vinca minor
•  Ivy
•  Creeping Jenny
•  Dichondra ‘Silver Falls’

Check out this guide for more inspiration on ways to combine thrillers, fillers, and spillers inside containers for your garden.

5 Tips for Combining Thrillers, Fillers, and Spillers

Consider Your Plants’ Care Requirements

Mix plants that need similar growing conditions in terms of sunlight, soil type, and water. For example, ferns and agave grow in different climates. Not only will they look completely out of place next to each other, but will also struggle due to the drastic difference in soil type and watering schedule. However, ferns will be happier and look better next to astrantias or bromeliads. 

If herbs are more to your liking than flowers, take a look at my recommendations for the best herbs to grow on your windowsill.

Take Size Into Account

You don’t want plants to steal the spotlight from each other, or outgrow their neighbors. Similarly, you don’t want your thrillers to be too tall, or they will create a disproportionate gap that the fillers won’t be able to fill.

Don’t forget about the size of your pot. To maintain a sense of scale and balance, your display should not be taller than three times the height of the container.

Understand Color Theory

The way you use colors can make or break your arrangement, so choose them wisely. Bright colors will make your arrangement look bigger, while darker colors have a shrinking effect.

The best container displays use complementary colors, so aim for a mix of yellow and purple, orange and blue, or red and green. Add a splash of white or pastel colors to make your display pop. And if you’re up for a challenge, ombré--where similar colors of different hues fade into each other--is a fantastic look if you make it work.

You can also create monochromatic flower displays but use red carefully. It’s a tricky color that can make your arrangement look dull and flat, so it’s always best used in combination with other colors.

Use Foliage To Create Interest

Different foliage textures create contrast and prevent a boring, repetitive design. For example, if your thrillers have spiky leaves, use fillers with rounded leaves to break the monotony. Foliage also creates continuity during the times when no flowers are blooming in your arrangement. Use plants like grasses, alchemilla, ivy, sedum, and coleus to provide interest throughout the season.

Continuity vs Repetition

All elements of your floral arrangement must work together. The easiest way to achieve that is through repetition, whether it’s color or shape. However, repetition can quickly become monotonous and uninteresting.

Avoid using any design element more than twice. For example, if your thrillers have variegated foliage, use either variegated fillers or spillers, but not both. For monochromatic displays, use different hues, play around with different leaf and flower shapes, and repeat the color in the foliage as well as the flowers. 

CONCLUSION

Using thrillers, fillers, and spillers can transform any container into a veritable showpiece. So mix and match your favorites from our list of recommendations, and your floral arrangement will look like it was designed by a pro.