Zinnias are annual flowers ranging from single-blooming daisy-like flowers, similar to the original zinnias first noticed in Mexico, to more elaborate hybrids that possess a wide variety of bloom color, size and petal shape. Heirloom varieties include tenuiflora and peruviana, with single flowers of bronze, yellow and red. The zinnia angustifolia "Crystal" series, one of the best zinnias for heat tolerance and mildew resistance, grows to a height of 18 inches with 1 1/2-inch orange-centered yellow and white flowers.
Zinnias grow quickly from seed, and do best when planted directly into well-drained soil that receives full sunlight. Double and semi-double flowered zinnias are widely available and include the eye-catching "Candy Cane" variety, with its 3-inch-wide double flowers atop 24-inch stems. Color combinations range from a yellow and pink mixture to white streaked with bronze. Semi-double flowering zinnias include the rare lime-colored "Envy," featuring a visible center surrounded with multiple petal rows. The popular "Lilliput" series has beehive-shaped double flowers in shades of white, orange, purple, pink, red and yellow on 18-inch stems.
Compact zinnias, which attain a height of only 12-inches, are a response to the increased popularity of container gardening and smaller garden spaces. The "Profusion Cherry" and "Profusion Orange" zinnias are not only disease-resistant and heat and humidity tolerant, but require no dead-heading to encourage repeat bloom. "Red Spider" features 1-inch spider-like blooms in a striking red color. "Giant Cactus Double," a popular variety with 4 to 5-inch blooms in a wide range of colors, attains a 24-inch height. "Oriole," with its huge bright gold and orange blooms, is a show-stopper, attaining a height of 30 inches. "Big Red" and "Luminosa Pink" are especially suited to attracting butterflies.