Annual flowers like marigolds and black-eyed susans may only live a year, but their fast growth and bright colors add a quick jolt of color to any backyard garden or landscape. Don't just stick whatever catches your fancy into the ground. Although you can grow dozens of different annual species and hundreds of specific cultivars and hybrids, the right choice depends on factors like your landscape's soil conditions and sunshine levels.
Narrow down the hundreds of options available to you according to the amount of shade and sun in your garden. The majority of annuals thrive in sunny locations, but some annuals also tolerate shade. That includes impatiens and browallia for heavy shade and pansies and lobelia for light shade.
Pick the plants by height. Annuals typically range anywhere from a few feet tall to groundcovers that are only a few inches high. For the lushest look, pick several annual species in varying sizes to create a full, dense flower bed. For beds in the middle of an open space, place tall plants in the middle followed by consecutively shorter annuals as you approach the bed's borders. For beds against a wall, place the tallest plants in the back.
Select the plants according to their color. While you can start with the colors that you find personally appealing, most landscapers narrow their list of options by comparing the flowers' colors on a color wheel. For the most pleasing look, choose flowers that have complementary hues. Complementary colors are found on opposite sides of the color wheel (e.g. blue bachelor's buttons go well with yellow lantana)
Review which annual species or annual cultivars are recommended for your region's soils and climates according to your local Cooperative Extension office. Certain varieties are bred to thrive in specific soils and climates or to be resistant to diseases that are prevalent in specific regions. Your Cooperative Extension office can provide a comprehensive list.