Zinnia

Zinnias are primarily native to Mexico, where they were called “mal de ojos,” which means  “sickness of the eye.” Having a name like that probably wouldn’t make you want to run out and get this plant for your garden! Later, it was given the name Zinnia, in honor of Johann Gottfried Zinn, a German botanist and anatomist who wrote the first detailed description of the flower in the 1750’s. Today, Zinnias can be found in gardens all across the United States.

Zinnia is a genus of 20 species in the family Asteraceae.  The flowers come in a great variety of colors, sizes and shapes. They may be single, double, dome shaped, cactus flowered or pompon types, and grow anywhere from 6 to 36 inches tall. Flowers can be 2-6 inches in diameter, and exist in a huge range of colors, including chartreuse and multicolored. Zinnias also make excellent cut flowers.

Zinnias are usually grown from seeds, and they are one of the easiest plants to grow. They should be planted in full sun, with well drained soil and plenty of room for air to circulate. They do not like having their roots disturbed, so seeds should be sown in individual peat pots, or directly in the ground. Long, hot, dry summers are the best as Zinnias are quite tolerant of drought. If temperatures are below 50 degrees, Zinnias will not grow until it gets warmer.  Spent flowers should be deadheaded to prolong flowering, which will continue until frost.

Zinnias are very prone to powdery mildew, which is a fungus that can discolor, distort and wither the plant, and cause the leaves to fall off. Mild days with low humidity and cool nights are ideal for powdery mildew to grow, and it usually appears in late summer. For a time, the popularity of Zinnias dropped off, as gardeners did not want to take a chance of growing diseased plants. To help prevent powdery mildew, avoid the foliage when watering, apply fungicide, provide plenty of air circulation and make sure the soil is well drained.

The easiest way to avoid mildew is to plant mildew resistant species. These are species that are naturally resistant, or hybrids which have been bred to be resistant. Zinnia angustifolia is thought to be the original Zinnia that is native to Mexico, and it resists disease and drought. These have smaller flowers than the more widespread Zinnia elegans. Hybrids created by breeding these two species together have the best traits of each species. They tolerate heat, humidity and mildew and need no deadheading.

I’ve had Zinnias in my yard many times over the years, sometimes grown from seed, and some bought as plants. Though I did not realize it at the time, I’m pretty sure a lot of them were victims of powdery mildew. I don’t specifically remember the white patches, but I know the leaves fell off and the flowers withered. Now that I am aware of that, I will take steps to prevent mildew in the future.

Tags: annuals, Flowers, garden, powdery mildew, zinnia