Window boxes full of trailing plants create beautiful summer displays, and there is no lack of plants to select from. Garden centers and nurseries sell packs of bedding plants that bear prolific flowers all summer, and you can sow annual flower seeds in window boxes in spring. Ensure your window boxes have drainage holes, and fill the boxes with a lightweight, soilless potting mix. Water the plants regularly so that the soil remains moist — in hot, dry weather you may want to water twice a day.
Bedding Plants
Bedding plants typically provide temporary displays in garden beds, borders, hanging baskets, containers and window boxes. Million bells (Calibrachoa spp.) Is named because of its profuse blossoms, which also come in colors of yellow. Also called trailing petunia, million bells grows 4 to 9 inches tall and 6 to 24 inches wide, and prefers full-sun websites. Even though thousand bows grows outside year-round in U.S. Department of Agriculture plant hardiness zones 9 through 11, it’s generally treated as an annual. Another perennial usually grown as an annual bedding plant is hybrid tuberous begonia (Begonia tuberosa), which rises in USDA zones 9 through 11, that comes in forged, yellow-blooming varieties. Growing 12 to 18 inches tall and wide, depending on the number, hybrid tuberous begonia grows best in bright, partial shade.
Annual Flowers
Sowing annual flower seeds directly in window boxes avoids the bother of transplanting, and provides new displays each year. Nasturtium (Tropaeolum spp.) And creeping zinnia (Sanvitalia procumbens) are just two annual flowers that grow readily from seed sown in spring. Nasturtiums arrive in a range of flower colors, including yellow, and bushy or trailing forms that can grow up to 10 feet, depending on the variety. Creeping zinnia rises 3 to 6 inches tall and 9 to 18 inches wide, and contains yellowish to orange-yellow, daisylike flowers on weeping stalks. Both plants grow best in full sun.
Trailing Vines
Trailing vines create long, cascading displays from window boxes. Black-eyed Susan (Thunbergia alata), which rises in USDA zones 10 through 11, produces dark-throated, orange-yellow late-summer blossoms. Growing 3 to 8 feet long and 3 to 6 ft wide, black-eyed Susan does best in partial shade or full sun, but is deemed invasive in some places. Below USDA zone 10, treat this vine as a warm-season annual by planting seeds in spring. Yellow mandevilla (Pentalinon luteum), that rises in USDA zones 10 through 11, attributes trumpetlike, neon yellow summertime blooms on stems up to 8 feet long. Growing best in full sun, yellow mandevilla is an evergreen vine.
Cascading Perennials
Perennials develop in window boxes year old, and several are trailing plants. Creeping Jenny “Aurea” (Lysimachia nummularia “Aurea” ), which rises in USDA zones 3 through 9 is named because of its yellowish foliage and bright yellow, cup-shaped, early summer blooms. This vigorous perennial can spread aggressively and can be invasive in some places. “Aurea” rises 3 to 6 inches tall and 12 to 18 inches wide, and thrives in partial shade or full sun, though in partial shade that the leaf is lime green. “Trailing Yellow” gazania (Gazania mitsuwa “Trailing Yellow”), that rises in USDA zones 8 through 10, bears bright yellow, daisylike flowers on plants 6 to 8 inches tall and 3 to 4 feet wide. Preferring full sun, “Trailing Yellow” can also be deer-resistant.