By Andrew Bunting
PHS Vice President, Public Horticulture
Planting a Spring Window Box
For many people who live in cities or urban areas, often their only chance to garden might be in a window box. There are many streets I walk down in Philadelphia where it seems that every row house that might not have any front yard whatsoever will often have a window box adorning every first-floor window. Each one unique and beautiful in its own presentation, window boxes are a wonderful way to express yourself, celebrate the change of seasons, and garden in a small space. If you have window boxes – whether on the first floor, second floor, hanging off a deck, or elsewhere -- now is a great time to kick-off the gardening season with a colorful new design.
You will need to use plants that can take lower temperatures with the nighttime temperatures sometimes dipping below freezing. While this does limit the ultimate selection of plants, there are still many choices available that will be great additions to your window box and thrive during these cool periods.
For my demonstration, I used a window box on the north side of my house which is three feet long, ten inches wide and about twelve inches deep. My window box is wooden, but I have seen attractive ones made from plastic, metal, and other materials. There are only two prerequisites for window boxes: the ability to hold soil and the ability to drain, so be sure you have some holes in the bottom of it!
For my window box I used some plants I had on hand from other projects earlier in the season. For upright grass-like foliage I used the sedge, Carex testacea ‘Prairie Fire’ and flanked it with ornamental vegetables with filigreed purple foliage—'Purple Peacock’ kale. For additional purple foliage, I added some lettuce called ‘Merlot’, then to spill over the edges of the window box I added white variegated ivy called Hedera helix ‘Glacier’. For some height and an element of whimsy, I took just-pruned branches of my normally coral-stemmed dogwood, Cornus sericea ‘Cardinal’, which are now a chartreuse-green and combined them with the red-stemmed Cornus sericea ‘Elegantissima’ in the box. While these stems are not growing, they will stay viable until the boxes need to be dismantled for summer annuals in May.
During a time where we may not have access to our normal candidates for window boxes, make use of some plants you already have on hand or even consider dividing perennials in the garden, like Heuchera, Acorus, and evergreen ferns.