Window boxes provide additional planting space around the home while adding curb appeal to the house. If a window box is located in a partly shaded area, there is still enough sunlight to grow most plants. The shallow root space and fast drying ground supply two hurdles that are overcome by choosing plants that do not develop deep roots and perform withstand drought conditions.
Perennial flowers return in the origin every spring, attracting the window box to existence with interesting colours. Cascading hopflower oregano (Origanum libanoticum) grows best in U.S. Department of Agriculture plant hardiness zones 4 through 10, reaching 1 to 2 feet tall and wide with fragrant, pale-green leaves forming paper-lantern shapes on arching stems. The tiny, rose-pink flowers appear from summer through autumn attracting butterflies and hummingbirds to the window box. “Chi Chi” sturdy pink petunias (Ruellia brittoniana “Chi Chi”) create dark-green, narrow leaves covering the 24-inch-tall comes topped with pink flowers from summer until the end of fall in USDA zones 7 through 10. This tall plant looks great when implanted near the back of the window box.
Evergreen plants keep their leaves through the winter, providing year-round color. The dwarf asparagus fern (Asparagus densiflorus “Nana”) grows in dense, round clumps 15 inches tall and wide with glowing lime-green, fine needle-like leaves at USDA zones 9 through 11 with white flowers blooming in the spring. “Limelight” licorice plants (Helichrysum petiolare “Limelight”), in USDA plant hardiness zones 9 through 11, climb 1 to 2 feet tall covered with chartreuse-green, velvety leaves and tiny white blooms. This licorice-scented plant spreads up to 6 feet wide unless back to a sensible size.
Semi-evergreen plants remain colorful and keep their leaves all year long unless exposed to freezing temperatures. They lose their leaves in winter. “Bowles’ Mauve” wallflowers (Erysimum “Bowles’ Mauve”) create clusters of fragrant pink blossoms blooming from spring until the end of summer on an erect, shrubby, gray-green plant 18 to 24 inches tall and 15 to 18 inches wide in USDA zones 6 through 11. Pink Texas skullcap (Scutellaria suffrutescens) form a 4-inch-tall mound spreading 15 inches wide with green leaves and rose-red flowers appearing all summer long in USDA plant hardiness zones 7 through 10. This plant need watering until it is established and producing new growth. “Wild Thing” fall sage (Salvia greggii “Wild Thing”), at USDA zones 6 through 10, rises coral-pink flowers lasting from spring until the end of autumn on 2- to 3-feet-tall stems. This blossom attracts hummingbirds, and the plant requires clipping to control the length of the stems.
Succulent plants create thick leaves and stems, which store moisture, as an adaption to growing in dry conditions. “Blue Spruce” stonecrop (Sedum reflexum “Blue Spruce”), at USDA plant hardiness zones 3 through 11, creates small, blue, evergreen leaves resembling blue spruce needles and yellow summer flowers on 8-inch-tall stalks. This easy-care plant spreads up to 18 inches wide. Calico kitty crassula (Crassula pellucid “Variegata”) rises 12-inch-long trailing stems covered with variegated leaves in rose, pink, cream and green colours. Find this succulent near the front border of the window box so that the stem may hang over the rim.