How to Grow Zinnias
In This Article — Care | Varieties | Pruning | Propagating | Overwintering | Pests and Diseases
Zinnias are a gift from hot climates but gardeners everywhere can easily grow them. They are fast-growing, warm-season annual flowers that bloom with abandon and require only minimal care.
Although we traditionally think of zinnias as bold, hot-palette colors, there are new ones being introduced every year, including some cool whites. There are tall, short, and spreading varieties and they all are very easy to grow, withstanding some of the worst growing conditions.
Zinnia elegans has lance-shaped, rough leaves, but other varieties can have broader, less scratchy leaves. It has a wide variety of bold-colored, rounded flowers. There are dwarf varieties and tall varieties that will grow up to 4-feet tall. Flowers can be daisy-like, double, cactus-flowered, or a formal-looking dahlia-like flower.
Plant zinnias in spring; they are hot weather lovers and will sit and wait for the temperature to warm up before really starting to grow.
Zinnias are one of the few plants that are true annuals. Many plants labeled as annuals are actually perennials that are only hardy in the warmest hardiness zones, but zinnias will be annuals everywhere.
There are spreading and dwarf zinnias that only grow about 6 to 8-inches tall, and the classic zinnia elegans can reach 4-feet tall.
Zinnia plants can take a few weeks to become established, but once it warms up, expect them to bloom from late spring right through fall. The vibrant, tropical colors of zinnias work well in a hot border, picking up the hues of other reds and oranges. They are also nice for adding dramatic color to a container.
The tall zinnia elegans is still a favorite for the back of the border, but new varieties, like the Thumbelina series, grow only about 6-inches tall and make great choices as edging plants or in containers.
You really want to plant zinnias in a spot with full sun. You will get the most prolific blooms in a sunny spot and it will help to keep the leaves dry and thwart powdery mildew before it starts.
The only real soil requirement is that it be well-draining. Zinnias roots do not like to sit in damp soil and excess moisture improves their chances of getting powdery mildew. It helps to have a soil pH in the neutral range, but it’s not mandatory.
Zinnias are very drought tolerant and don’t usually need any supplemental watering. If your soil is poor, you can add some compost to give the plants a boost, but they will grow in even bad soil.
Temperature and Humidity
It doesn’t matter how hot the summer gets; zinnia plants just keep on blooming.
Zinnias are easy-going plants, needing only occasional feeding with a well-balanced fertilizer.
- ‘Zahara’: has large flowers, and is mildew resistant
- ‘Dreamland’: displays double flower heads on a compact dwarf plant
- ‘Envy’: boasts semi-double chartreuse flowers and is 30-inches tall
- ‘Orange Star’: offers orange flowers and is a bushy dwarf
You can deadhead zinnias for a longer blooming period, but it’s not absolutely necessary. They may pause flowering for a while, but they’ll start up again.
There are a couple of ways to propagate zinnias: by division, using already established plants, or with cuttings.
Zinnias are annuals, and the only way to keep them going through the winter is to dig them up and bring them inside.
Common Pests and Diseases
It is rare for zinnias to be bothered by insects and most four-footed animals show no interest in them.
Some varieties can be very prone to powdery mildew. It’s ugly, but it’s unlikely to really harm your plants. To cure, clip back the parts of the plant that are affected. Then, apply a fungicide with neem oil, potassium bicarbonate, copper, or sulfur.
|Botanical Name||Zinnia elegans|
|Plant Type||Annual shrubs|
|Mature Size||1-4 ft. tall, 12-18 in. wide|
|Sun Exposure||Full sun|
|Bloom Time||Late spring through first frost|
|Flower Color||Pink, purple, yellow, orange, lavender, white, red, and green|
|Native Area||South America, Mexico, southwestern United States|