The Best Cascading Flowers for Window Boxes

When it comes to window box planting, there is a rule of thumb that many are aware of; it’s known as the “thriller, filler, and spiller” rule, which gives the window box a balanced, beautiful design. Cascading flowers for window boxes, the “spillers” of the triune, are called such because they “spill out” of the window box in a glorious tumble of greenery. Be sure to plant them consistently to get a well-balanced window box. Done right, a window box overflowing with green goodness adds color, texture, and life to your home.

What to Consider When Selecting a Spiller

How do you determine which spiller would be best for your window box? Answering the following questions will help you choose:

  • Which plant profile would match the architectural style of my house? (Example: if you have a farmhouse, you might want your window box to look more overgrown, whereas a mid-century modern home might look best with a more restrained, streamlined plant aesthetic.)
  • Which spillers would look good with the thrillers and fillers I’ve chosen? Think complementing colors (like coral and lime green) and adding textural interest.
  • Are my window boxes going to be mostly in sun, shade, or a balance of both?
  • Do I want to switch out my spiller with the new season, or do I want a spiller that blooms year round?
  • Do I want a green or flowering plant?
  • How much time and effort do I want to spend maintaining my window box garden? (For a zero maintenance window box garden, try fade-resistant artificial hanging flowers and vines)

Spillers for Sun, Shade, and in Between


Calibrachoa (full sun)

Creeping Phlox (full sun)

Verbena (full sun)

Sedum (full sun)

Moss Rose (full sun)

Morning Glories (full to partial sun)

Creeping Jenny (full to partial sun)

String of Pearls (full to partial sun)

Petunia (full to partial sun)

Bacopa (full to partial sun)

Licorice Vine (full to partial sun)

Lobelia (full to partial sun)

Creeping Jenny



Ivy (full shade)

Fuchsia (full to partial shade)

Pilea (full to partial shade)

Bolivian Jew (full to partial shade)

Asparagus Fern (full to partial shade)

Vinca Vine (full to partial shade)

Nasturtium (partial shade)

Silver Falls (partial shade)

Asparagus Fern


Sun or shade:

Sweet Potato Vine


Wire Vine

Sweet Potato Vine

More Spiller Tips

  1. Sweet potato vine is a great, tried-and-true spiller, but it easily overtakes a window box and all the other plants in it. Keep it trimmed back, or plant Creeping Jenny instead to get the same trailing green vine effect, but without the aggressive growth.
  2. When deciding on a spiller, check out your local nursery and peruse their potted plant arrangements to see which spillers will grow (and look) best with other plants. Find an arrangement you’d like to copy, and make a note of the plants used to create the same look!
  3. When choosing the amount of plants to plant for your window boxes, use the “rule of thirds” design rule, which posits that we visually break up a space into thirds. Selecting an odd plant number (three, five, seven, etc.), with a third of the plants being spillers. This will make the overall arrangement more visually appealing.
  4. Fire up your window box imagination with these inspiring photos on our Window Box Inspiration Board!
  5. If you don’t want to mess with maintaining live plants in your window box, try some of our outdoor-rated artificial flowers and plants. For example, try adding Artificial Morning Glories to your window boxes for fade-free blooms all year ’round (and with their natural look, no one will ever know they’re not real!) Choose from pink, red, white, yellow, and purple flowers.
  6. Keep your window boxes from damage and rot with a long lasting and durable planter liner.
  7. If you travel a lot or simply don’t want to spend a lot of time watering your plants, add a water reservoir to your window box; it will keep the soil evenly moist for up to two weeks at a time (and about one week in hot summer months)!
  8. If you don’t have a green thumb, consider these hard-to-kill plants when choosing what to use in your window boxes.

All Your Window Box Needs (and Inspiration!) Right Here

Whatever stage your window box gardens are in—designing, planting, or replanting—we can help you with it all! For questions or orders, visit us at or call us toll-free at 1-800-896-0978.

Photo credits (top to bottom, left to right): @wildcottonphoto, Hooks and LatticeNourish and NestleMichael SpragueSpencer MeansTerence FairclothDeborah SilverKevinJudy Van Der VeldenPaige FillerBriarCraft, and Karen DeSanno. Blog featured image: Spencer Means

3 replies
  1. Heather
    Heather says:

    These tips are great! I am saving this for the spring. Window boxes will make a huge difference but we definitely have varying light depending on what area of our house.

  2. Anne H Martin
    Anne H Martin says:

    I love your list of window box “spillers” and the breakdown of sun vs. shade. Do you have similar lists of “thrillers” and “fillers”?


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