Window box flowers and plants need to be good container plants that can deal with ever changing sunlight. Plants for a window box can be tall or draping, depending on the style of window planter. You can even mix draping plants and tall plants in a window box for variety.
Blue Daze, or Evolvulus glomeratus, is from the Convolvulaceae, or morning glory, family. It is an evergreen perennial that gets 2 to 3 feet wide and a foot tall. Leaves have a fuzzy light gray look and are egg shaped. Flowers are funnel shaped, 1 inch wide, and blue or lavender. Plant a blue daze plant in full sun and well-drained soils. Propagate via seed or softwood stem cuttings.
Wild columbine, or Aquilegia canadensis, is from the Ranunculaceae, or buttercup, family. It is an easy to grow perennial that attracts hummingbirds. It can get 2 feet tall and 1 foot wide. Flowers are bell like and 1 to 2 inches long, red or yellow, with fern like leaves 4 to 6 inches wide. Plant a wild columbine plant in any sun situation and in any type of soil. Propagate via seed or dig up seedlings and replant
Impatiens, or Impatiens wallerana, is from the Balsaminaceae, or balsam, family. It is an easy to grow perennial grown as an annual. It will attract hummingbirds. Impatiens gets 8 to 24 inches high with a variety of flower colors. It has plenty of blooms and is very easy to grow. Plant this plant in moist well drained fertile soil with partial shade to partial sun. Propagate via cuttings or by seed.
Zinnia, or zinnia elegans, is from the Asteraceae/Compositae, or aster/daisy, family. It is an annual that is drought resistant and will attract butterflies and hummingbirds. Zinnia gets up to 30 inches tall with various colored flowers, from 2 inches across up to 6 inches across. Plant a zinnia plant in well drained rich soil in full sun or some cultivars allow for some shade. Propagate via seed after last frost of the spring.
Moss rose, or Portulaca grandiflora, is from the Portulaceae, or purslane, family. It is a drought resistant annual. Moss rose gets 6 inches tall and 12 inches wide with bright green thick leaves and rose like flowers 1 inch across. Plant a moss rose plant in well drained soils in full sun. Propagate via seed.