How to Plant and Grow Zinnia

Zinnia is an extremely tough annual with varieties of many shapes, sizes, and colors. The plant's vibrant blooms are a favorite among pollinators, such as hummingbirds, bees, and butterflies, who love to hover around the flowers and drink their nectar. While tall zinnia suit cottage and cutting gardens, the plant's lower-growing, mounding, or spreading varieties work well in containers. Additionally, shorter cultivars are lower-maintenance than their taller counterparts, as they require less frequent deadheading. Regardless of their height, zinnia plants add vivid visual appeal to any garden in need of a bold splash of color.

Where to Plant Zinnia

Tall zinnia varieties are perfect for the back of a garden border or a cutting garden. Gardeners often grow clumps of several zinnia plants together for a stunning effect. Shorter varieties have more of a mounding appearance and are attractive front-of-the-border options. Regardless of your chosen variety, plant zinnia in an area where it will receive full sun. It can flower in partial shade but will produce fewer blooms and be more vulnerable to disease. Zinnia grows equally well in a garden bed or a container, but the soil must be well-draining. If it isn't, the plant will be susceptible to root rot.

Zinnia's strong, long stems make the plant a fantastic candidate for cut flowers. Since zinnia blooms come in a rainbow of colors, they're enchanting additions to floral arrangements. Tall varieties are especially excellent for cut flowers, with options like cactus- and quill-type blooms boasting long, narrow petals and pom-pom-type blossoms that look like little spheres.

How and When to Plant Zinnia

Zinnia are warm-weather annuals that don't like cold weather or cold soil, so they shouldn't be set out or sown outdoors before the soil warms in spring.

For an early start, sow seeds indoors in pots filled with moist seed-starting mix 4 to 6 weeks before the last spring frost date. Cover them with 1/4 inch of soil and put them in a sunny window until they are ready to transplant. They germinate in 7-10 days and should be at least 4 inches tall before being transplanted outside. When working with zinnia, never handle the plant by the stems—only by the rootball.

To successfully sow seeds in a garden bed, wait for warm weather, then cover them with 1/4 inch of soil. The seeds germinate in 7-10 days. Once the seedlings have grown to 2 inches tall, thin them to 8 to 24 inches apart, depending on the variety.

Zinnia Care Tips

Zinnia is a relatively low-maintenance plant when grown in its preferred conditions.

Light

Because the plant originates from prairie settings, zinnia prefers full sun. This environment nurtures the best bloom development and helps keep the plant dry.

Soil and Water

Native to grassland areas, established zinnia is a tough plant that handles drought well. However, young plants need to grow in moist soil, so water deeply a few times a week, being careful not to overwater. Zinnia doesn't handle wet roots well.

Even though zinnia grows best in well-drained soil high in organic matter, it's tolerant of poor soils, including hard clay. Amend poor soil before planting for the best flower production.

Temperature and Humidity

Zinnia seeds germinate between 70°F and 75°F. After germination, the plant's preferred daily temperature is 75°F to 85°F, although 65°F at night is acceptable. Zinnia isn't fond of high humidity but will tolerate it.

Fertilizer

In both garden bed and container settings, zinnia benefits from a dose of 5-5-5 fertilizer when its flowers form. Fertilizer is especially important in containers filled with a soilless potting medium. The occasional liquid fertilizer application helps zinnia bloom consistently throughout the growing season. In all cases, follow the product instructions for the proper quantity of fertilizer.

Pruning

Deadhead spent blooms regularly to keep a tidy appearance and encourage additional zinnia blooms. To encourage branching and more flowers in tall varieties, pinch the growing tip from young plants. Note that pinched plants will be shorter and may bloom later. No additional pruning is needed as zinnia is an annual that must be replanted yearly.

Potting and Repotting

The shorter varieties of bedding zinnia are excellent container plants. Use a container at least 12 inches wide and 12 inches deep, and fill it with well-draining garden soil enriched with compost. Sow a few seeds outside in a container immediately after the weather warms, thinning as needed later. Alternatively, start seeds indoors in a container, then move the container outside once the weather is warm enough. Avoid growing the tallest zinnia types in pots.

Pests and Problems

One common problem with zinnia is root rot, which is prevented by planting in full sun and not overwatering. When not planted in full sun, zinnias may also be afflicted by powdery mildew, which appears as a white powder on the plant's bottom leaves. While this pesky fungus probably won't kill the plants, it does diminish their beauty. The best control method for powdery mildew is prevention; look for resistant zinnia varieties and account for plenty of airflow space around the plants.

Leaf spot and blight are two other common diseases found in zinnia. Similar to powdery mildew, these conditions are caused by fungi. Control methods are the same: Remove any debris from the base of the plants to keep them clean. Additionally, Japanese beetles love zinnia. Gardeners have turned to beetle traps for years with mixed results. If there are just a few of these insects on your zinnia, hand-pick them off.

How to Propagate Zinnia

Saving zinnia seeds is an excellent way to start next year's plants. Zinnia seeds are often sold as mixes, so you don't have to worry about seedlings being identical to the parent plant. To harvest your own seeds, remove the spent blooms from your zinnia and collect the small, arrowhead-shaped seeds from each petal by shaking the dried flower heads in a paper bag. Store the seeds in a dry, warm area until the weather warms in spring.

Zinnia can also be propagated in water with cuttings in about 3 to 4 weeks. In spring, cut 4 to 6 inches from the tips of stems and remove the leaves from the bottom half of the cuttings. Put the cuttings in a glass or jar with enough water to cover the bottom half of the cuttings, making sure some leaf nodes are underwater. Place the container in a warm area with bright light but not full sun. When a root structure develops and the weather warms, transplant the new zinnia to the garden.

Types of Zinnia

'Benary's Giant Orange' Zinnia

Zinnia elegans 'Benary's Giant Orange' is an excellent cut flower with large, 4-inch-wide, double orange blooms. This zinnia variety grows to 38 inches tall and 2 feet wide.

'Magellan Mix' Zinnia

Zinnia elegans 'Magellan Mix' has double blooms in a wide range of shades, including red, pink, yellow, orange, and white. It grows to 16 inches tall.

'Parasol Mix' Zinnia

Zinnia elegans 'Parasol Mix' bears fully double, petal-filled flowers in various shades. The plant grows to 12 inches tall.

'Cut and Come Again' Zinnia

Zinnia elegans 'Cut and Come Again' is especially free flowering and bears double flowers in a range of bright colors on a 4-foot-tall plant.

'Profusion White' Zinnia

Zinnia elegans 'Profusion White' is an early-flowering selection with good disease resistance and white flowers that bloom all summer. It grows to 18 inches tall and 10 inches wide.

'Scarlet Flame' Zinnia

Zinnia elegans 'Scarlet Flame' offers double red flowers on a vigorous, 42-inch-tall plant.

'Zahara Coral Rose' Zinnia

Zinnia marylandica 'Zahara Coral Rose' bears big flowers in a soft shade of pink. It's a disease-resistant, heat-loving plant that grows to 18 inches tall and wide.

'Zahara Starlight Rose' Zinnia

Zinnia marylandica 'Zahara Starlight Rose' is a compact (to 18 inches tall and wide), award-winning selection with white flowers that have a distinct pink blush. It's very disease-resistant.

'Zahara White' Zinnia

Zinnia marylandica 'Zahara White' is a compact selection that grows to 18 inches tall and wide with big white flowers. It's a disease-resistant, heat-loving variety.

'Zahara Yellow' Zinnia

Zinnia marylandica 'Zahara Yellow' produces big flowers in a bright, sunny color on a disease-resistant, heat-loving plant that grows to 18 inches tall and wide.

Zinnia Companion Plants

Spider Flower

Once temperatures warm, spider flower sprouts to 4 feet or more, buds very quickly, and produces large balls of flowers with fascinating, long seedpods. The annual typically self-seeds prolifically, so you only have to plant it once. Because it develops surprisingly large thorns, it's best to keep spider flower away from walkways. Plant seedlings in spring after all danger of frost has passed. Spider flower does best in moderately rich, well-drained soil. Be careful about fertilizing, or you'll have extremely tall, floppy plants. Group spider flower plants in clusters of six or more for the best effect.

French Marigold

French marigold produces frilly flowers, and some boast a distinctive "crested eye." The plant grows roughly 8 to 12 inches high with a neat growth habit and elegant, dark green foliage. French marigold does best in full sun with moist, well-drained soil and will flower all summer. The plant may reseed, returning year after year in spots where it's happy.

Salvia

Many gardens have at least one variety of salvia growing in them. All attract hummingbirds and are great picks for hot, dry sites where you want tons of color all season. Most salvias don't like cool weather, so plant them outdoors after all danger of frost has passed.

Garden Plans for Zinnia

Butterfly Garden Plan

These breathtaking flowers are irresistible to butterflies. Blossoms offer nectar to adult butterflies, while leafy foliage nourishes the larvae. Butterflies are sun-loving creatures, as are the plants in this design, so be sure to site this garden where it will receive six or more hours of sun daily.

Hot Summer Garden Plan

Heat and humidity are no match for this hot-summer garden plan! It features a mix of annuals and perennials that flourish in steamy weather. Plus, their consistently blooming flowers in colorful hues seem to get brighter as temperatures climb.

French Kitchen Garden Plan

Our French-style kitchen garden features a central diamond-shaped bed and four larger raised beds with wide brick pathways running between them. The raised beds are filled with a mix of vegetables, herbs, and edible flowers that are beautiful and bountiful. Additionally, shrubs and perennials comprise a hedge around the entire garden to complete the French-inspired design.