Flowers may be striped, speckled, or multicolored, and they may be single, double, or semi-double. Flowers on doubles may look like cactus flowers, dahlias, or simple buttons. Hundreds of cultivars make it easy for the gardener to choose ones that suit many landscape purposes. Sizes range from mere groundcovers to plants over three feet tall. Sandpapery, lance-shaped leaves provide a perfect backdrop for the colorful flowers.
Zinnias are easily started from seeds. Plant them where they are to grow in full sun and in fertile, well-drained soil. They can also be set out from young seedlings provided they are handled carefully, for they are very sensitive to root disturbance. Add organic matter if your soil is very sandy and lacking in nutrients or if it has a high clay content and poor drainage. Sprinkle about two pounds of slow-release fertilizer such as 6-6-6 per 100 square feet of planting area. Scatter the seeds according to package directions, and do not let the bed dry out until seedlings have emerged.
After the seedlings are two or three inches tall, thin to allow plenty of space between plants for good air circulation. Powdery mildew can afflict zinnias, especially in hot, humid climates or in beds where plants are packed so closely together that the foliage stays wet for long periods of time. Critters such as spidermites, mealybugs, and aphids may be troublesome, but can usually be held to acceptable levels by an occasional strong spray of water to the affected areas. If it becomes necessary, treat with a mild pesticide such as pyrethrin or insecticidal soap.
After plants are up and growing, add mulch to retain moisture and inhibit weed growth. Water during lengthy dry periods. Deadhead spent flowers, and cut often for bouquets. A sprinkling of fertilizer during midsummer will keep plants growing vigorously. Midsummer is also a good time to plant a new bed of zinnias for spectacular fall color.
As winter approaches and the zinnias are in imminent danger of being killed by frosts, allow a few of the flowers to dry on the plant. Then snap them off and keep in a dry place until the following spring. One flower head will most likely yield all the plants you could possibly need. With a few more in the bag, all your friends can be treated to a generous package of seeds for their gardens. Remember that hybrids may not come back true to the parent. A bit of seedling variation, however, can add surprise and interest to the zinnia bed.
Kinds of Zinnias
According to GRIN Taxonomy for Plants, published by the USDA Agricultural Research Service, there are thirteen species of Zinnia. However, of these, there are many cultivars as well as interspecific hybrids that expand the palate exponentially.
The most familiar species is Zinnia elegans, which is the tall, upright type with which most people are familiar. Many cultivars and series are available, including 'Dreamland', 'Magellan', 'Ruffles', 'Oklahoma', Benary Giant, Peter Pan, Giant Cactus, and others. Most of the series are available in color mixes or in single colors.
Zinnia angustifolia (narrow-leaf zinnia) is a low-growing species that is suited for the front of the flower bed and is available in colors of orange, yellow, and white. Particularly popular as a landscape zinnia, this species requires little or no deadheading, is extremely heat tolerant, and is highly resistant to diseases that plague other species. The Crystal series and the Star series offer dense masses of color throughout the summer. ‘Crystal White' was an All America Selection in 1997.
Zinnia tenuifolia bears red, one-inch, single scarlet flowers with dark centers. Thin, widely spaced petals curve like a spider's legs, giving it the common name of red spider zinnia. The durable plants reach 18 to 24 inches tall.
Zinnia haageana is a species that is smaller than Z. elegans. This very heat, drought, and disease tolerant species bears one- to two-inch wide bi-colored flowers in a range of spicy colors including gold, purple, red, white, and orange. Sometimes they are called "Mexican zinnias." The Persian Carpet series is a colorful mixture of fiery colors while the cultivar ‘Chippendale' sports bi-colored blossoms of mahogany with a yellow or orange rim.
Many of the zinnias on the market today are interspecific hybrids. A popular hybrid is the Profusion series, a cross between Zinnia elegans and Zinnia angustifolia. All demonstrate a high degree of disease tolerance. The Profusion zinnias bloom throughout the summer in dense, compact mounds. Flowers are available in a range of colors including white, orange, cherry, apricot, and red. Work continues with the hybridizers, and new colors and sizes are introduced regularly. ‘Profusion White', ‘Profusion Orange', and ‘Profusion Cherry' are All-America Selection winners. Profusion zinnias are now available in knee-high plants that grow 20 to 24 inches tall and spread about a foot wide.
Three zinnias were chosen as All America Selection winners in 2010. From the Zahara series, the cultivars ‘Double Zahara Fire, ‘Zahara Starlight Rose', and ‘Double Zahara Cherry' performed well in full sun gardens across the United States. Pictures below are compliments of AAS. These interspecific hybrids grow about 12 inches tall and have high resistance to leaf spot and mildew diseases.
Uses in Floral Design
Zinnias are excellent flowers for cutting and enjoying in bouquets and floral arrangements. For best results, choose long-stemmed cultivars such as ‘State Fair'. Generally speaking, a plant that grows more than 18 inches tall is a candidate for the vase. Cut flowers just as they start opening and place the stems in water immediately. The best cutting time is in the early morning before flowers have had a chance to loose moisture and while they are fully hydrated. Arrange in simple vases or baskets and enjoy for about a week.
Zinnias dried in silica jel can be enjoyed for a much longer time. They can also be dried by hanging upside down in an airy place out of direct light. Doubles are best for drying by this method because they hold their shape better than singles. Expect them to change colors somewhat and to lose some of their brilliance.
Whichever zinnias you choose to grow will add charm to your garden, and frequent cutting will lend color to your interior spaces. Adding to the allure are the butterflies that are sure to abound when the zinnias bloom. With so many colors, sizes, and flower forms from which to choose, what's not to like about this group of flowers?
Thanks to Dalethegardener for his image of Zinnia angustifolia and to bigcityal for Zinnia elegans 'Dreamland' mix.