Zinnias are annual flowers among the favorites in American garden flowers, loved for its sturdy and colorful blooms. They are grouped in three different classes ranging in height from tall (to 30 inches), intermediate (to 20 inches), and dwarf (to 12 inches). The flowers come in almost every color except blue. Zinnias require full sun and rich, fertile soil. They grow best in hot, dry climates. Uses include beds and borders as well as container plantings. Taller varieties make a great back drop in a planter bed.