Shade-tolerant, compact annual, bulb and perennial flowers brighten up ready-made or handcrafted window boxes located in shady spots of the garden. Some flowers tolerate partial shade, and bloom well when they receive two to fours hours of direct sunlight per day. Other flowers tolerate full shade and bloom when they get only two hours of direct sunlight each day.
Shades of Violet and Blue
Annual wishbone flower (Torenia fournieri) produces trumpet-shaped, bicolor pale violet and dark blue blooms from early summer through the first frost. Flowering well in partial shade and full shade, wishbone flower also offers oval, light green, toothed leaves. Wishbone flower cultivar colors include pink, rose, burgundy, lavender and white.
Rose-Red Spring Blooms
Spring-flowering annual phlox (Phlox drummondii) tolerates partial shade, and bears fragrant, trumpet-shaped rose-red blooms. In areas with hot summers, annual phlox declines and stops flowering but sometimes returns in fall. For the best effect over the growing season, grow annual phlox with other window box plants.
Winter Flowers in Warm Climates
Cyclamen (Cyclamen persicum) is a winter-flowering bulb for growing in window boxes in U.S. Department of Agriculture plant hardiness zones 9 through 11. Growing well in full or partial shade, cyclamen features white, pink, red, violet or lavender blooms and dark green leaves that often have silver blotches or veins.
Flame violet (Episcia cupreata) cascades from window boxes in partial shade or full shade. This tropical perennial grows in USDA zones 10 through 12, and it can be grown as an annual in lower USDA zones. Flame violet is named for its yellow-throated, scarlet-red or orange flowers, and it has wrinkled green leaves flecked with purple and copper.
Long-Blooming in Full Shade
Also called busy Lizzie, impatiens (Impatiens walleriana) is a bushy plant with succulent stems that bears flowers in shades of white, pink, rose, orange, red, lilac, purple and bicolor. Blooms appear spring through frost in partial shade and full shade. Grown as an annual plant in areas of the U.S. that experience frosts, impatiens is hardy in USDA zones 10 through 11.
Angel Wings and Scarlet Blooms
Shiny green leaves like angel wings and drooping scarlet blooms are the decorative features of begonia Dragon Wing Red (Begonia 'Bepared'). Tolerating partial shade and full shade, Dragon Wing Red grows as a perennial in USDA zones 10 through 11. In lower USDA zones, use it as an annual to brighten window boxes.
White and Sunset Colors
Tuberous begonia (Begonia spp. Tuberosa Group) is a bulb that offers blooms in many shades including red, pink, orange, yellow and white, depending on the cultivar. Hardy in USDA zones 9 through 11, tuberous begonia can be treated as an annual in cooler cliamtes. Grow this plant in partial shade for the best results because it doesn't grow well in full shade.
Trailing Yellow Cups
Creeping Jenny 'Aurea' (Lysimachia nummularia 'Aurea') produces long stems covered in rounded yellow leaves that tumble from window boxes. Bright yellow, cup-shaped flowers appear in early summer. Also called moneywort for the shape of its leaves, 'Aurea' is a perennial that's hardy in USDA zones 3 through 9, and grows best in partial shade.
Providing ferny, grayish-green leaves and heart-shaped, crimson flowers on long, nodding stems, the perennial flower bleeding heart 'Adrian Bloom' (Dicentra 'Adrian Bloom') grows well in partial shade. Blooms appear late spring through summer. A perennial in USDA zones 3 through 8, 'Adrian Bloom' prefers cool climates and doesn't grow well in areas that experience hot, humid summers.