How to Plant, Grow, and Care For Zinnia Flowers
Are you thinking of adding some color to your garden by adding some Zinnia flowers? Zinnias come in a variety of different colors, and are easy to both plant and care for. But there's some tricks you'll want in your back pocket to make sure they flourish. In this article, gardening and flower expert Taylor Sievers walks through every step you'll need to successfully plant, grow, and care for Zinnia flowering plants.
If there’s one flower staple in the home garden I had to choose, then zinnias would have to be it! These heat-loving Mexican natives are easy to grow, low maintenance, and produce a jazzy pop of color all throughout the summer.
Zinnias can have versatile applications in landscaping and home gardens as long as you have a warm, sunny spot on your property. Plant a low-growing Zinnia angustifolia along a landscape border, a unique two-toned Zinnia haageana variety in a patio container, or a giant-flowered Zinnia elegans variety as a companion plant in your vegetable garden! None of these species will disappoint when it comes to cheeriness.
Are you looking for a flower that’s easy to sow and grow? Well, zinnias are the answer. As long as you plant your seeds or transplants after your last expected frost, then your zinnias will be off to the races. They grow relatively fast, with seedlings sprouting within days. The best part? Zinnia plants are givers. Cut off faded blooms and these highly productive plants will be churning out more blooms for you to enjoy!
Plant Type Herbaceous Annual
Plant Family Asteraceae
Plant Species elegans, angustifolia, haageana
Plant Genus Zennia
Native Area North America, South America
Hardiness Zone USDA 9-11
Tolerance Heat, Drought Resistant
Sun Exposure Full Sun
Watering Requirements Low
Maturity Date 75-90 Days
Growth Rate Fast
Plant With Insect Pollinating Veggies
Don’t Plant With Plants That Like Cool Weather
Soil Type Well-Draining
Plant Spacing 6-12 inches
Planting Depth 1/4 inch
Plant Height 8 inches – 3 feet
Attracts Butterflies, Bees, Hummingbirds
Pests Aphids, Mealybugs
Diseases Downy Mildew, Leaf Spots
Zinnias were thought of as relatively uninteresting when the Spanish conquistadors first traveled through Mexico in 1519, but since then the zinnia has become a bright, cheery, and easy-to-grow staple in the home garden. Claire Shaver Haughton’s book Green Immigrants: The Plants that Changed America gives an excellent account of the history of the zinnia, which can be summarized thus:
The zinnia began as a prolific plant with small daisy-like flowers in colors of dingy purple and dull yellow. The Aztec name for the zinnia translated to “eyesore,” so when the Spanish trekked through Mexico in the 1500s, the plant was then called “mal de ojos.”
In the 18th century, a young German doctor named Dr. Gottfried Zinn began collecting and studying wildflowers, and a friend of his that happened to be the German ambassador to Mexico sent him some seeds of the “mal de ojos” that had remained relatively insignificant since Europeans first set eyes on it a few hundred years prior. By 1759, Dr. Zinn had died and this new flower was named “zinnia” in his honor.
The flower became somewhat popular in European gardens and was nicknamed “everybody’s flower,” “poorhouse flower,” and “garden Cinderella.” In the 1880s, the French began experimenting with zinnias and eventually produced a dwarf form that was rather adaptable. This led to further experimentation with zinnia breeding. In 1886, a double zinnia in bright, clear colors with a larger flower was produced. It was then that plant breeders in the United States began to take interest in the zinnia.
Sixteen species of zinnia were discovered after U.S. breeders began to take notice, and all of these species were found to be indigenous to Mexico. It was surmised that most of the European species were derived from Zinnia elegans and Zinnia haageana. Known for being a “weedy” species, the zinnia naturally had sturdy stems and a slightly pungent odor that discouraged insects, and was also mostly tolerant to any type of soil or climate, though it flourished in rich soil and warm weather.
United States Popularity
By 1920, a man named Luther Burbank had produced a dahlia-like zinnia in California. After Burbank died, his head gardener, William Henderson carried on the zinnia research. Eventually, William Atlee Burpee bought the Henderson Seed Company in the 1940s and moved the zinnia research to a farm he specifically purchased for zinnia experimentation, due to the original location being too near Pacific fogs, which were not ideal for a plant that loves sunny and warm weather.
Burpee began an extensive breeding program focused on hybridizing zinnias. The matter was proving difficult, as he found that he could force some zinnia plants to become tetraploids, but could not produce a tetraploid plant with fertile seeds.
Tetraploids are plants with double the number of chromosomes that are formed when the plant undergoes some sort of sudden shock, like freezing or extreme heat. If the seeds of a tetraploid plant prove fertile, then the breeder will be able to produce plants with larger and more complex flowers, obviously a desirable trait for a plant breeder and seed company.
The struggle was concerning, but suddenly, in 1948, in row 66 of Burpee’s Santa Paula farm, a freak zinnia was discovered. Nicknamed “Old 66,” this wholly female zinnia had a flower head that looked like pincushions filled with pin-like stigmas, but the plant had no petals and no pollen-laden stamens. However, the plant was able to fertilize with some of the best of Burpee’s male-flowering zinnias.
Ten years later, after much experimentation and selection, the first-generation of F1 hybrid zinnias were established and went onto the market. Old 66 was the mother of all these new zinnias!
Today, zinnias come in many shapes, sizes, and colors. Some of the most popular colors are pink, yellow, red, and even green. You can find giant, mini, cactus-like, pompon, and ruffled zinnias. Some grow 3 ft tall while others grow only 6 inches tall. The state of Indiana deemed the zinnia its state flower in 1931 until it was suddenly uprooted by the peony in 1957, a decision that was not without controversy. Regardless, zinnias are a cheery favorite in home gardens today!
Propagation of Zinnia
Just like cockscomb, the best way to propagate zinnias is by seed. Seeds can be started indoors 4 to 6 weeks before your estimated last frost. Plant seeds at a depth of ¼” and place them in a warm space, with a preferred temperature of 75 to 85 degrees F.
Zinnia seeds need darkness to germinate. Seeds will sprout rather quickly when given the right conditions, sometimes even within 24 to 48 hours! However, expect sprouting in 3 to 5 days. Transplant the seedlings into the garden when they are 3 to 5 inches tall and water well.
To direct sow into the garden, plant seeds 6 to 12 inches apart in a row and plant at ¼” depth. Zinnia is also a great candidate for broadcast sowing, but make sure to lightly rake the seeds into the soil to promote quick germination.
Plant seeds or transplants into the garden or into a pot after your last frost. You can plant successions of zinnias up until the middle of the summer for continuous blooms! If you know when your expected first frost will be in the Fall, you can count back about 60-90 days (depending on the variety you are growing) to determine when your last possible planting date should be during the summertime.
How to Grow
Plant zinnias in full sun (at least 8+ hours per day). These plants will thrive in hot, sunny conditions. In fact, if planted in shady areas the plants will become leggy, produce fewer blooms, and are more prone to mildew.
Excessive fertilizer application can promote mildew on zinnias. Providing a well-balanced (mostly equal parts of nitrogen, phosphorus, and potassium) fertilizer in a dry, granular form when preparing the bed is often all that is needed for this plant to grow.
Pinching the plants when they are about 6 inches tall will promote long, straighter side branches and a bushier plant. However, if you are regularly deadheading the plant (clipping off faded blooms), making a deep cut into the plant will also promote more branching without the initial pinch at 6 inches.
If you want to keep your plant blooming, make sure to deadhead regularly. Leave some flowers on the plants if you would like to save seed, but be aware that hybrid zinnias will not produce seeds true-to-type (exactly like the parent plant).
Some zinnia varieties with larger flower heads may tend to sprawl and thus need to be supported. Commercial zinnia growers often use flower netting to support stems, but for the home gardener, it may not be necessary.
Planting closer together will allow the stems to be supported by the adjacent plants, but be aware that tighter spacing may also promote mildew, due to poor circulation of air. Zinnias are usually considered annuals and will return year over year if taken care of properly. They are drought tolerant annuals, and can thrive with minimal moisture.
When and How to Harvest Zinnias
If your goal is to harvest zinnia blooms for a flower arrangement, then you should cut the blooms after they have fully opened and a few of the yellow, star-like stamens have begun to appear. Even then, your zinnia may not be ready to harvest, because the upper part of the stem must be sturdy to prevent wilting in the vase.
The best way to identify the right time to harvest is by doing the “wiggle test.” Simply grab the zinnia stem about a foot down from the flower head and give a gentle shake. If the flower head seems to flop back and forth, then it is too early to cut the stem. Wait a few days and try again. If the stem feels sturdy and the flower head stays put as you shake the stem, then it is ready to cut! Cut at the base of the stem you’re harvesting or cut just above 3 to 4 side shoots if you’re cutting the main stem. This will promote further branching.
If you want to harvest and save seeds, wait until the flower head has faded and the brown, flake-like seeds have formed on the flower head. Store the seed in a cool, dry place until you’re ready to plant.
Varieties of Zinnias
Below are some of the most popular varities of Zinnias that you’ll likely consider planting in a home garden setting. We’ll look at the most popular varieties, as well as what what flower color you can expect from each type once planted.
Plants grow between 1 to 3 feet tall with large blooms. The most widely grown variety is the “Benary’s Giant” series, with 4 to 5-inch full blooms that are prolific and mildew resistant. They are available in 13 colors.
‘Uproar Rose’ has stunning, large, rose-colored blooms and is well-branching. The ‘Queen’ series has become very popular because the colors appear in antique shades that are all the rage, with shades of rose, orange, and blush fading in with lime.
‘Zowie!’ is unique with its bicolor gold and magenta petals that stand out in the garden. ‘Oklahoma’ zinnias come in a range of colors but the blooms are much smaller, topping out at about 2 inches in diameter.
Plants in this species are used mostly in borders, containers, and hanging baskets due to their low-growing nature, with dwarf varieties as low as 6 inches tall. Some varieties can be as tall as 3 feet, however. The ‘Crystal’ series is a carefree, single-petaled variety that comes in orange, white, and yellow. This variety tops out at 10 inches. The ‘Star’ series is vigorous with star-shaped flowers and is downy mildew resistant.
This species can grow up to 2 feet tall with smaller flowers (about 1-2” across). Many of the flowers are two-toned, which makes for a stunning display of color in a flower bed. ‘Aztec Sunset’ produces 2-inch flowers in a range of colors from red, yellow, orange, and even a bicolor flower of orange and maroon. ‘Soleado’ has bright, cheerful blooms of orange and yellow with a mahogany ring around the center.
Pests and Diseases of Zinnia
While zinnias are relatively low maintenance, they are very susceptible to powdery mildew. Powdery mildew appears as a matte, whitish haze on the leaves usually in late summer or in crowded plantings with poor air circulation. The best way to avoid powdery mildew is to increase spacing between plants.
Alternaria leaf spot and bacterial leaf spot are two other common diseases in zinnia that cause brownish splotches or spots on the plant, usually starting from the bottom leaves and spreading upwards. During wet weather, these diseases will thrive. Affected foliage can be removed and destroyed (do not put in your compost pile) or you can apply a copper fungicide during periods of wetness to reduce the advancement of the disease. Always follow label instructions when using fungicides.
To prevent outbreaks of disease on your zinnias, make sure you have planted them in full sun. Leaf spot diseases are more prevalent in partial shade. Water your zinnias at the base of the plant rather than overhead, and water in the morning so that any water that’s splashed onto the leaves can dry throughout the day. Rotate zinnias within your garden each year. Also, clear away and destroy any diseased plant material from the previous season. Do not save seed from diseased zinnias, as some leaf spot diseases can be transmitted via seed.
Aphids, mites, and leaf miners can sometimes be an issue for zinnias. A forceful stream of water applied to the zinnia plants can sometimes knock these small pests off the plant.
One insect not mentioned in many sources about zinnias that I have had trouble with in the past is Japanese beetles. These beetles will chew on mainly the leaves of the plant, leaving a skeleton of leaf veins behind. They seem to come rapidly and then disappear just as rapidly, so when they come to visit my garden I like to pick them off and throw them into a bucket of soapy water rather than spray them.
Zinnias are excellent pollinator plants that will attract butterflies, bees, and hummingbirds. Be aware that the more petals the variety has, the harder it is for pollinators to extract nectar. So, often the big fluffy double blooms are not ideal for a pollinator patch. Because zinnias attract pollinators, they are an excellent companion plant for vegetables that require insect pollination.
Zinnias are also excellent cut flowers that provide beautiful color to summer bouquets. Zinnia flowers can also be dried in silica gel and used in dried flower wreaths in the Fall and Winter.
Frequently Asked Questions
Why are my zinnia blooms sparsely single-petaled?
This is a conundrum amongst many growers, especially with the scabiosa-type cupcake zinnias. One of the reasons that your zinnias are mostly sparse singles is due to genetics, and the other reasons are due to environmental factors.
It’s been found that in milder climates with ample moisture that this is less common, so the best advice is to water your zinnias well and plant them into good soil in full sun. Any stress may cause the plant to show its ugly side.
Why do my zinnias wilt immediately after being cut?
The first thing you should examine is whether your zinnia bloom was ready to cut in the first place. Perform the “wiggle test” by gently shaking the stem of the plant.
If the flower head flops too much, then you need to wait a few days before harvesting. Also, a good sign is when you see several of the yellow star-shaped stamens begin to appear in the center of the flower. The wiggle test is especially important for the zinnias with giant flower heads, as the flowers can be somewhat heavy.
Do I need to stake or support my zinnias?
Sometimes zinnias can flop over if not supported, but for the most part, if zinnias are planted in a group planting, then there is no need to stake them. Commercial cut flower growers will often use flower netting in order to ensure tall and straight stems.
However, as a home gardener, you will likely enjoy the way your zinnias naturally grow. Pinch your zinnia plants when they are six inches tall just above a set of leaves to produce a bushier plant. Remember to clip off spent blooms frequently so the plant will shoot out more blooms for you to enjoy.
If you’re looking for a long-lasting, low-maintenance, and colorful flower to grow in a sunny location in your garden, then no look further than zinnias! These cheerful blooms are easy to sow and grow. Cut blooms off all summer to bring inside for a pop of color on your dining room table. Or, watch as butterflies, bees, and hummingbirds galore flit to and fro throughout your zinnia patch. This flower is a must-grow for beginning gardeners, kids, and veggie gardeners. You won’t be disappointed!