Zinnia: Shiny and Cheerful Flowers

Zinnia flowers are some of the easiest to grow in a garden. Not only are they low maintenance, but they also attract pollinators and come in a variety of shapes, sizes, colors, and growth habits. If you want cut-and-come-again flowers, zinnia has you covered. If you want a pseudo perennial flower bush to accompany your annuals, zinnia plants do that too!

Not only are there tons out there to choose from, but zinnias are also easy-going and grow in raised beds, in-ground, or even in containers. They’re drought-tolerant and perfect for a spring and summer garden. Planting seed is easy. With semi-fertile, well-draining soil, you’re covered. 

Where I live, most vegetable gardens are accompanied by two flowers: zinnias and cosmos. Master gardeners in the area swear by zinnia plants for attracting butterflies to the garden. Outside this region, they are a mainstay. You will fall in love with them!

So let’s talk about zinnias and how to care for them.  

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Quick Care Guide

Benary’s Giant, lilac variant, is a gorgeous bloom. Source: McAli333

All About Zinnias

The zinnia is a member of the Asteraceae family, which includes daisies, asters, marigolds, and other flowering plants. They have many common names, all related to the hundreds of cultivars that exist within their 20 or so species. They’re native to Mexico, South America, and the southwestern United States and were first classified in the 1700s by Johann Gottfried Zinn, a German botanist.

Varying zinnia plants have different growth habits. Some have single, erect stems. Some are bushy. Some have single flowers, and some have double flowers. For these, zinnias form what appears as a single flower head but is actually made of small fertile flowers in a central ring that is surrounded by petal-shaped infertile flowers. One easy distinction between two major species is that Zinnia elegans has a tall, erect habit while Zinnia angustifolia creeps and spreads through the garden.

Their soft, light green leaves covered in trichomes seem perennial, but that’s because they self-seed readily. They’re great for a spring or summer garden, the vegetable patch, and they’re also lovely in pollinator landscapes. They can get out of hand, though. It’s important to exercise proper pruning and care when growing them. 

Zinnias were thought to be a poor man’s flower when they were first introduced to European elites. This is because of how common and easy to grow they are. However, I think zinnia flowers have quite a regal and stately presence in the garden. They are excellent alongside my melon vines or in cut flower bouquets.

Types of Zinnia Plants

Yellow Star zinniass are a lovely single-petal variety. Source: audreyjm529

In the last section, we mentioned the distinction between Zinnia elegans and Zinnia augustofolia. Let’s add to that with this: there are three types of zinnias. These are determined by the kind of zinnia flowers that grow. There are single-flowered plants, semi-double, and double-flowered ones. Before you order seed packets, let’s talk about several of cultivars organized by flower type.

Single-flowered zinnias

These zinnias bloom a flower with a visible center and a single line of petals. 

• Red Spider: with narrow red petals and yellow visible centers, this compact plant is great for attracting pollinators.  
• Crystal White: another bushy variety with small white flowers and yellow centers. Quite delicate related to other cultivars. 
• Star Zinnia: the single-petaled flowers of star zinnia come in varying shades of white, orange, and yellow. A bushy variety with disease resistance. 
• Mexican Zinnias: stunning variegated orange and yellow petals give these zinnias a wild look. Each bloom emerges from a low-lying flush of foliage. Great cut flowers. 
• Soleado: another wild-looking bushel with orange blooms. 

Semidouble-flowered zinnias

Semi-doubles have multiple petal rows with visible centers. Many are tall varieties. 

• Benary’s Giant: one of the taller varieties that produce 3’ stems ideal for vases. Find a mix for numerous rows of orange, yellow, red, pink, and purple flowers. 
• Zahara series: includes Zahara starlight and Double Zahara Fire zinnias that top out at 12 inches and are powdery mildew resistant and self-deadhead. 
• Queen Lime Series: includes Queen Lime Zinnias that are large flowers that range from pink to green and even orange and yellow. 
• Big Red: this zinnia grows an extra large bloom that is a cross between a dahlia and a double flower. An intense pop of red wherever they’re planted. 
• Purple Prince: this mildew and disease-resistant variety has brightly colored purple blooms that grow on stems up to 3 feet tall. 
• Thumbelina series: these semi-double/double flower hybrids bloom all season long, and top out at 12 inches tall. Flower heads are varying shades of pink, yellow, white, and red. 

Double-flowered zinnias

Zinnias with double flowerheads have multiple rows of petals and a seemingly inaccessible center. Sometimes confused with dahlias. 

• Cactus Zinnia: perhaps the most interesting zinnia out there? The quilled petals of this plant are 3 to 6 inches across and come in shades of pink, orange, white, yellow, and red.
• Profusion series: a commonly available powdery mildew resistant series with lance-shaped foliage. For peachy blooms try Apricot profusion. Up to 12 inches tall. 
• Dreamland series: this series of dwarf double petal zinnias forms dense mats of red, cream, yellow, and pink flowers.
• California Giant: one of my absolute favorites! Large 3 to 5-inch bright orange to scarlet flowers grow atop a 30 to 36-inch stem. 

If you can’t decide which to grow, try the California Mix Zinnia Seeds we have in our Epic Gardening shop. 

Zinnia Care

Semidouble flowered zinnias don’t completely obscure the center of the flower. Source: Francisco Soto

Whether you’re growing Zinnia elegans or another species, their needs are similar enough that we put this information in one place. Let’s talk about how to nurture them in your summer garden every year. 

How to Plant Zinnias

When you plant zinnias, you need to know where you want them and when to plant them. Because zinnia seedlings are subject to transplant shock, it’s not recommended you try to start them indoors to transplant elsewhere when they’re mature enough. Planting in peat pots might help, but you may still slightly disturb the roots. Zinnias do best if they’re sown directly after the last frost date in late spring. Broadcast them into areas of your garden that need a pop of color or a pollen attractant. As they emerge, thin them to 6 inches apart for dwarf varieties and 12 inches for others. 

Sun and Temperature

Zinnias thrive in warm climates in areas exposed to full sun. They also thrive in partial shade areas but need at least 6 hours of sunlight per day. Their ideal temperature range is between 74° F and 84° F (or 23° C to 28° C). Zinnias are annuals. As the summer wears on and the heat increases, most will remain. Some are sensitive to heat and die back if they aren’t already established. They do not tolerate frost. Plant them in spring in full sun, and watch them bloom through summer into fall. In some areas, zinnias remain in the garden until the first frost of early winter. 

Water and Humidity

While zinnias are drought-tolerant, they do need regular watering. Give them at least 1 inch of water per week after they sprout and as they get established. Grow zinnia in soil with good drainage, and provide irrigation via soaker hoses or drip tape below the plant. This prevents fungal spots that can occur when zinnias are watered overhead. 

Soil

Mexican zinnias are often variegated in color. Source: PMillera4

The base rule for easy-going zinnias is to provide them with well-drained soil. Soils high in organic matter support zinnia flowers better than poor soils, but oftentimes, zinnias will grow anywhere. The soil should retain some moisture, but not so much that it remains wet for long. Excess moisture makes Zinnia elegans and other species susceptible to diseases. Plant zinnias in slightly acidic soil at 5.5 to 7.5 pH. 

Fertilizing

In rich soil, you won’t need to focus on fertilizing zinnias. However, in poorer soils provide regular fertilizer. Spread a slow-release granular fertilizer high in phosphorous two to three times in the spring and summer growing season. Alternatively, a soil drench of compost tea applied every two weeks or so in spring and summer works. I’ve had an easy time with established Zinnia elegans that got very little fertilizer in the years they were growing. 

Pruning Zinnias

When you grow zinnia, pruning zinnia flowers is paramount. When the first bloom fully opens, prune it off at the bud joint to promote more blooming later in the season. While not all zinnias are cut-and-come-again, those that are appreciate consistent pruning of blooms. Cut these at the leaf node and put them in colorful floral arrangements. When you do this, the area where you cut will now branch off and produce two stems for zinnia flowers to grow on. Deadhead them as they fade in fall or winter. Unless you want tons of zinnias in that spot next year, know that deadheading prevents them from taking over. While zinnias are annuals, they’ll self-seed and emerge in that spot in spring. 

Prune the foliage of your zinnia plants to promote good air circulation. Zinnias are prone to a lot of diseases that thrive in congested garden areas. Pruning is your first line of preventing these diseases in your garden. 

Propagation

While you can let zinnias pop up in areas of your garden annually, you can also collect seeds when you deadhead old flowers and remove those to be planted directly in early or late spring. Or, if you have at least 100 days or more until the first frost arrives, sow another patch for more flowers later in the season. I hang on to a bag of seeds and wait for spring to sprinkle them around annuals for an extra pollen source. Zinnias work well in blank spaces of your garden, too, where other plants may have failed, or in spots that need an extra pop of color that lasts all season long. Remember to pinch back seedlings to 12 inches apart when they reach a few inches tall. This keeps them from choking each other and other plants out. 

Troubleshooting

The Profusion series has stunning double petals. Source: rachelgreenbelt

Zinnias are great plants that grow quickly, attract pollinators, and provide your garden with vibrant, cheery blooming petals for months. However, there are a few things to be aware of when you grow them.  

Growing Problems

If you try to sow zinnia seed indoors and then plant them outdoors (even in peat pots), they may experience transplant shock. Instead, simply broadcast seeds in your garden. 

Most issues associated with zinnias involve too much of a good thing. Yes, sow seeds densely. But space them as they grow, and deadhead them after their petals fade. This prevents an overwhelming amount of zinnias in the following year. Give excess seeds to your friends!

If you plant zinnias too late, they won’t have time to bloom before the frost date hits, or they may not have time to take off before it gets too hot for seeds to germinate. Here in the south, it’s easy to be just slightly behind on planting when heat waves roll in early. The general rule of thumb is they need cool to temperate weather to germinate, and the flowers need at least 100 days before the frost to put out lovely blooms. 

Pests

You’ll deal with basic pests on zinnias. Aphids are little pear-shaped insects that hang out on the undersides of leaves, sucking the sap from zinnia foliage. Knock them off your plants with a strong stream of water. Follow up with a light mist of neem oil spray applied over the green parts of the plant. If they are on the petals, remove the flower they’re feasting on. But don’t spray the blooms with neem. Apply neem in the morning before the sun has risen, and do not apply in temperatures at or above 90° F (32° C). 

Spider mites look like tiny yellow or red dots that move around your zinnias, feasting on plant sap. In infestations, you’ll see webs wound around the plant. They thrive in conditions that are warm and dry. Water regularly to prevent them. To treat them, wipe the plants down with a damp cloth and follow up with insecticidal soap. Reapply once every several days. 

Whiteflies are tiny white moths that also consume plant sap. They are common in greenhouses and on houseplants, and they sometimes strike outdoor plants too. Hit them with a strong stream of water. If they continue to feed, the honeydew they secrete can kill your plant. Use insecticidal spray such as pyrethrin as a follow-up if water doesn’t take care of them. Wipe down the leaves, removing the honeydew and their eggs in one fell swoop.

Diseases

Powdery mildew is the most common disease that affects zinnias. Most of the time, planting them in the right spot, keeping the soil adequately moist and not wet, and removing any mildewed foliage keeps it in check, or prevents it. If it can’t be controlled with selective pruning, try neem oil. Use the same instructions from the last section to apply it.  

Alternaria leaf spot, bacterial leaf spot, and cercospora leaf spot are all caused by either fungal or watermold pathogens that thrive in warm, wet conditions. Watering at the base of zinnias, rather than overhead, prevents wetting leaves. If left out of hand, the wet, dark spots caused by these pathogens can lead to bacterial wilt as they spread to other parts of the plant. You can selectively prune affected leaves to promote better air circulation, then with a fungicide such as sulfur fungicide or copper fungicide to kill the pathogens. Prevent with neem oil to provide an extra layer of protection, but don’t apply neem oil within a week of either fungicide.

Aster yellows is a disease that affects all plants in the Asteraceae family. It’s transmitted by leafhoppers that carry the disease on their body as they hop from plant to plant. Control them to prevent its spread. Once a plant is infected with aster yellows and takes on the yellowing appearance and warped growth, remove them and either burn them or bury them deep in your compost pile so other insects can’t feed on them, perpetuating the cycle. Remove any weeds from the area, and do the same with those. 

Frequently Asked Questions

Each zinnia is an explosion of beautiful color. Source: Muffet

Q: Does zinnia come back every year?

A: In the garden, zinnias work seem like perennials, but are actually self-seeding annuals. As long as conditions are right, they’ll die off in fall or winter and return in spring. 

Q: Does zinnia need full sun?

A: Yes! Full sun, and sometimes partial shade with at least 6 to 8 hours of sun per day is needed to grow zinnia. 

Q: How long will zinnias bloom?

A: Their flowers bloom in summer and remain until frost arrives. 

Q: Is zinnia easy to grow?

A: One of the easiest! If you’re new to gardening, try growing them in a pot. 

Q: Can I just scatter zinnia seeds?

A: Absolutely. Scatter them within planted garden beds, or sow a single row of them alongside your garden. 

Q: Do zinnias need to be deadheaded?

A: Unless you want them to spread everywhere, yes, deadhead each spent flower. 

Q: Do zinnias like lots of water?

A: When they’re mature, they can handle some drought. But if you have the ability to provide about an inch of water per week, that’s best!

Q: What month do you plant zinnia seeds?

A: It depends on your regional frost dates. Plant zinnia seed in spring after the last frost date with at least 100 days before the fall or winter frost arrives.