Zinnia

Zinnia is a genus within the sunflower family, Asteraceae, and belongs to the tribe Heliantheae. These plants are known for their single, long-stemmed flowers that typically have 12 petals and display a wide range of vivid colors. The genus was named after Johann Gottfried Zinn, an 18th-century German scientist. Zinnias are naturally found in scrublands and dry grasslands stretching from the Southwestern United States down to South America, with the greatest variety of species occurring in Mexico.

The group includes annuals, shrubs, and sub-shrubs. Most species grow upright, though some have a spreading, mounding habit. Heights usually range from 10 to 100 cm (4 to 40 inches). Their leaves grow in opposite pairs and are generally stalkless, varying in shape from linear to oval and in color from pale to medium green. The flowers are composite, made up of ray florets surrounding a central disk of florets, which may be a different color. These blooms can appear as a single row of petals, a dome shape, or something in between. Colors include white, chartreuse, yellow, orange, red, purple, and lilac. Each disk floret has five petals enclosing five stamens. When the petals open, the style pushes pollen upward, making it available to insects like hoverflies. Nectar at the base of the floret attracts long-tongued bees and butterflies. As the style grows, it splits into two branches, with the stigmatic surfaces maturing to receive pollen.

The genus name honors Johann Gottfried Zinn (1727–1759), who collected seeds of *Zinnia elegans* in Mexico.

Zinnias are easy to grow and produce heavy, brightly colored blooms. Their petals can be single (one row with a visible center), double (many rows hiding the center), or semi-double (several rows but a visible center). They are annuals usually sown directly in the ground, as they dislike transplanting due to fragile roots, though they can be started indoors 4-6 weeks before planting if moved before roots fully develop. They prefer full sun and adequate water, grow quickly, but are sensitive to frost and die after the first autumn frost. Deadheading encourages more blooms.

Accepted species include *Zinnia acerosa*, *Z. americana*, *Z. angustifolia*, *Z. anomala*, *Z. bicolor*, *Z. citrea*, *Z. coahuilana*, *Z. elegans*, *Z. flavicoma*, *Z. grandiflora*, *Z. guanajuatensis*, *Z. haageana*, *Z. juniperifolia*, *Z. maritima*, *Z. marylandica*, *Z. microglossa*, *Z. oligantha*, *Z. peruviana*, *Z. purpusii*, *Z. tenella*, *Z. tenuis*, *Z. venusta*, *Z. zamudiana*, and *Z. zinnioides*. Formerly included species are now placed in *Glossocardia* and *Philactis*. *Zinnia elegans* (also called *Z. violacea*) is the most familiar species, native to warm regions of Mexico. It has lance-shaped, sandpapery leaves and grows 15 cm to 1 meter tall. *Zinnia angustifolia* is another Mexican species with a low, bushy habit, linear leaves, and smaller, often single flowers in yellow, orange, or white. It is more resistant to powdery mildew than *Z. elegans*, and hybrids like the 'Profusion' cultivars combine this resistance with intermediate appearances. Zinnias are favored by butterflies and hummingbirds.

Zinnias are popular garden flowers due to their wide range of colors and shapes, tolerance of hot summer temperatures, and ease of growing from seed. They bloom all summer and will reseed themselves. They thrive in fertile, humus-rich, well-drained soil in full sun. Over 100 cultivars have been developed since selective breeding began in the 19th century. *Zinnia peruviana* was introduced to Europe in the early 1700s, and *Z. elegans* followed around 1790.