Gardening Sweet Spots
By Donna Hessel
I have always admired homes with window boxes. I don’t know why, except that these homes seem to extend a more cordial welcome than those without that complement. If you agree, here are some suggestions as to how to add them to your windows, or keep current ones looking great all year ‘round.
Starting with New Boxes
It’s best to purchase boxes made from rot-resistant materials. They should be sturdy enough to hold the weight of soil and plants. Keep in mind that soil and water will make the boxes heavier. Most important: make sure they have drainage holes.
The best wooden boxes are made of treated redwood or cedar. A heavy plastic or metal liner will extend the life of a wooden box. Fiberglass is expensive, but will last a long time. You can disguise inexpensive plastic boxes with the “spiller” plants you include. If you prefer a less formal, English-cottage appearance, opt for a coir-lined hayrack. Most window boxes look best if they are a little longer than the window width, so measure before you shop.
Read the directions that come with your window boxes before hanging them. Note that the brackets should keep the boxes away from your siding, which prevents potential water damage from trapped water. Brackets should be slightly longer than the width of the box to include this spacing. Make sure the top of the box is a few inches below the window (especially if your windows open outward) so plants won’t obscure your view.
To reduce the weight of the boxes, use a filler of packing peanuts, foam pieces or sweet gum tree balls before you add soil and plants. Most annuals need only six inches of soil. You may have to water your boxes daily, especially if they are under eaves or gutters. Window boxes, like containers, dry out quickly. To reduce maintenance, choose drought-tolerant annuals that bloom over a long period and do not require deadheading. Include plants whose best feature is their foliage.
Planting Window Boxes
Decide whether you want your box to be seasonal or to last year-round. In our Northeast Ohio climate, year-round boxes should include a small, slow-growing evergreens such as a dwarf variety of boxwood. Evergreens that have bright new growth or change color in the fall are a bonus. Virginia creeper used as a spiller will turn red in the fall before it loses its leaves. While ivy doesn’t change color, it will provide year-round interest. Tuck in spring bulbs that bloom early in the season, such as crocuses, which are usually the earliest to bloom in yellow, white and purple. Try miniature daffodils, pansies or violas if your box is in the sun. Replace spent bulbs with colorful annuals for summer and in the fall, add garden mums, asters or flowering kale. Fill in with gourds or small pumpkins for seasonal interest. Tuck in some cut pine, holly or red berried branches in the winter.
Whether seasonal or year-round, follow the thriller-filler-spiller formula for best plant styling and selection. Note whether your box is in full sun, partial shade or full shade so you can select plants that will thrive. Full-sun plants need at least six hours of direct sunlight per day, and generally prefer warm afternoon sun. Part-shade plants need 4-6 hours of sun, while full-shade plants will grow with less than four hours of sun exposure per day.
Here are some additional tips that will assure successful boxes:
- Use a good potting soil on top of the filler in your box and mix in a slow-release fertilizer before you plant. Water with a water-soluble fertilizer every couple of weeks during the growing season.
- Avoid pairing flowers that need consistently moist soil with those that are drought tolerant. Since they will be sharing soil in the same area, they will all receive the same amount of moisture.
- To make sure one plant won’t overtake the others in your box, choose varieties with similar growth rates. This might mean pairing different colors of the same kind of plant—for example, planting three different colors of geraniums.
- Contrast is the key to designing a sensational color scheme. Choose plants with a variety of different shaped leaves and flowers, some with larger leaves and others with finely textured ones.
- The number of plants you’ll need to fill your window box depends on several factors including its size, what size plants you are starting with, and how big they grow. Grouping the plants you’ve selected together on a bench at the store will give you a good idea of how many will comfortably fit in your box.
- Before you shop, consider what colors you might want to use. Stay focused on your selected color scheme and don’t be swayed by all the color choices on the sale racks!
Colorful Foliage for Shady Boxes|
This photo is of a window box on the north side of my home that gets very little sun. The caladiums are a definite winner, no matter what color you
choose, and many new varieties are currently available. Choose colelus wisely, as some cultivars will take over the whole box! You can’t beat their color selections that will work with whatever else you choose. Long-blooming, no-deadheading-needed impatiens are a no-brainer, and with all their color choices, you can complement any color scheme. I have tried several types of spillers from ivies to silvery licorice, to chartreuse creeping jenny to variegated wandering jew. All will work well in a shady box. Ferns, sweet potato vines and miniature hostas are also good foliage choices. I think I might try heliotrope and sweet alyssum, which will trail, this year.
Other shade-tolerant plants to try are begonias, browalia, coral bells (many colors to choose from), torenia, asparagus or painted fern, brunnera, or purple oxalis. Shade-tolerant low-growing ornamental grasses are good fillers. A pegasus begonia has beautiful, big, multi-faceted leaves, but will grow tall.
Colorful Window Boxes for Sun
There are many choices for window boxes in sunny locations. Try celosia, geraniums, snap dragons, low-growing salvias, mini zinnias, lantana, Persian shield, euphorbia, marigolds (the slugs and pill bugs can’t get at them in window boxes) or nasturtiums. A short growing ornamental grass is a nice addition. Trailing plants such as black-eyed susan vine, ivy leafed geraniums, multi-colored calibrachoas (mini petunias) or trailing verbena are pretty and work with greener ivy vines.
If you like window boxes but don’t have appropriate windows to display them, set boxes on benches or tables on a
balcony, deck or patio; or hang hayracks with coco-coir liners on your deck railings for a similar look.
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Sources: Garden Gate Magazine, Online Newsletter. April 23, 2019. “Pretty View Year-Round” by Kristin Beane Sullivan.
Horticulture Online Newsletter. “Choosing, Hanging and Caring for Window Boxes” by Meghan Shinn, Updated March 22, 2022; Original May 31, 2018.
Proven Winners Online Newsletter, March 7, 2022 – Contributor: Susan Martin
Photos by Marie Elium, Donna Hessel and pexels.com.
