Plant greenery such as ferns with an upright growth habit, tall mondo grass species, smaller elephant’s ear species or arrowhead plants in the center of the container.
Arrange shorter upright-growing greenery around the center plant. Use short spurge species such as the Helena cultivar or lady ferns like Fancy Fronds. Intermix them with blooming plants.
Grow greenery with a vining or trailing growth habit around the edge of the container. Use English or Swedish ivy for this purpose. Or try ornamental sweet potato vine for something unusual-looking; it's available with a variety of leaf shapes and colors.
Plant taller upright greenery such as shorter varieties of New Zealand grass at the back of the container. In containers set in a corner or up against a wall, the upright greenery will serve as a backdrop for the other plants.
Intermix shorter upright greenery throughout the center of the container. Plant one or two spurge, lady fern, watermelon begonia or similar plants among the flowering plants to provide interesting texture.
Plant vining or trailing greenery along the outer edge in the front and around the sides of the container. Arrange the ivy, trailing watermelon begonia or sweet potato vines so they will grow over the sides of the container.
Use a taller upright greenery-type plant at the center of a rectangular container. Place foliage plants with an upright growth habit on each side of a taller blooming plant when a flowering plant is used as the center focal point. Use foliage plants that are shorter than the flowering focal point.
Place foliage plants such as rex begonias between the flowering plants along the length of the container. Rex begonias are available in a wide variety of leaf colors. They can be selected in shades that will complement the flower colors of the blooming plants.
Arrange vining or trailing foliage plants along the visible edges of the container. Plant them only along the outer edge of rectangular containers used as window boxes. Plant them along both sides of rectangular containers that are visible from both sides.