How to Plant Zinnia Seeds

Updated on 07/15/24

Reviewed by

items for planting zinnia seeds — The Spruce / Candace Madonna

In This Article

Types and Varieties
Before Getting Started
Growing Tips
FAQ

Working Time: 1 - 5 hrs
Total Time: 1 - 5 hrs
Skill Level: Beginner
Estimated Cost: $20 to $40

If you have dreams of growing an organic garden from A-Z, you may want to start at the end with some easy-growing, gorgeous zinnias. With broad blossoms, bright colors, and next to nothing to worry about ruining your tending efforts, zinnias are some of the easiest and most rewarding flowers to grow. Learn how to plant zinnia seeds for the best return and make a major impact on your garden or landscape this year.

Types and Varieties of Zinnia Seeds

Considering the height, color, and shape combinations, there are dozens and dozens of zinnia varieties to choose from. Since it’s so easy to collect seeds from zinnia plants, try sticking with heirloom or open-pollinated varieties that will produce reliable replicas year after year. Still, there are lots of options when deciding which zinnias to plant.

Zinnias come in a range of shape types, including varieties that resemble daisies or dahlias, tight blossoms in beehive shapes, small button blooms, and large floppy blossoms. As a quick, easy annual, tuck zinnias around other plants or make a full zinnia patch. Mix up height and color–have fun playing with the many options zinnias provide without having to cater to pickier plants.

Some eye-catching varieties to check out include:

‘Envy’: bright, chartreuse green blooms
‘Carousel’: multicolored and sturdy
Burpee ‘Rose Giant Cactus’: has a vintage feel and full, pointed petals
‘Will Rogers’: boasts shocking red, large blooms

Zinnias do best in full sun, so gather your collection of zinnia seeds, choose your space, and get ready to start your zinnias.

Before Getting Started

As a full-sun flower that likes warm weather, zinnias need the air and soil to be at least 70°F to germinate and begin to thrive. If you plan to transplant zinnias, make sure not to disturb the roots or allow plants to become rootbound. That doesn’t mean you can’t make the most of the growing season, though. You still have a choice between starting zinnia seeds indoors or sowing seeds directly outdoors.

What You'll Need

Equipment / Tools

Hand trowel
Hand transplanter
Garden shears

Materials

Zinnia seeds
Seed starting mix
Peat pots
Compost

Instructions

Materials and tools to plant zinnia seeds — The Spruce / Heidi Kolsky

Sow Seeds Outdoors

The easiest way to start zinnias from seed is to plant them directly in their final beds outdoors. It takes air and soil of more than 70°F to germinate well, so wait until spring to plant zinnia seeds.

Plant them about 1/4 inch deep right in the ground, spaced as much as your chosen variety needs, anywhere from a couple of inches to a couple of feet. Once they sprout, thin them carefully to encourage the strongest to thrive. Give enough space so that sufficient air flows around the mature flowers, preventing disease.

The Spruce / Heidi Kolsky
Start Seeds Indoors

If you want a jump on the growing season for some early spring color, start seeds in seed starting mix and peat pots about 6 weeks before the last frost. Once the soil is warmed enough for zinnias, plant the entire pot in the ground for an easy transition.

The Spruce / Heidi Kolsky
Maintain Proper Soil Conditions

Zinnias like well-fed soil, so some compost worked into the ground early in the season will give the soil an edge before it’s time to get the zinnia seeds or plants in the ground. Moisture is important in the early weeks, but make sure it doesn’t get soggy. Well-drained soil is a must to prevent problems.

The Spruce / Heidi Kolsky
Stagger Multiple Plantings

Depending on the variety, zinnias will last for around 2 months, so stagger multiple plantings in the garden to keep zinnia flowers in the garden from spring through fall. Some varieties bloom prolifically all season long. Heavy humidity might be your only obstacle to constant zinnias all summer.

The Spruce / Heidi Kolsky
Water Them Properly

Water and sunlight will keep your zinnias blooming fully and frequently. Too much water, however, will risk powdery mildew, one of the only diseases zinnias are susceptible to. Provide about an inch of water per week, through rain or irrigation. And, as with most plants, avoid spraying the foliage and flowers as much as possible and not at all during the heat of the day.

The Spruce / Heidi Kolsky
Shape the Plants

If you want full, bushy zinnia plants, pinch the top of the stems off of young plants. If you want to encourage tall zinnias, stake the largest so they don’t flop over.

Harvesting zinnias as cut flowers will also encourage full growth, telling the zinnia to keep producing blooms until some go to seed. Cut the stems above the leaf or bud nodes and new stems will keep growing and producing new blooms.

The Spruce / Heidi Kolsky
Save the Seeds

Once a zinnia plant is done, remove it and plant something else in its place. For heirloom varieties, let a few go to seed, and be sure to collect them so you'll have an abundance of zinnias next year. Try to save seeds from zinnia plants that are tucked behind others to avoid having dying zinnias as a focal point.

The Spruce / Heidi Kolsky

Tips for Growing Zinnias From Seed

Ideally, start zinnia seeds outdoors, but if your growing season is short, start them in biodegradable pots indoors so you don’t disturb the roots when transplanting them.
Follow the spacing requirement for the variety. Once the seedlings have emerged, thin them to the strongest plants to prevent overcrowding.
Keep the soil evenly moist at all times to get the seedlings off to a strong start. Always water at the plant base and avoid getting the foliage wet.
For a continuous bloom, seed zinnias repeatedly over the spring and summer.
Pinch the top of the stems of the young plant for a bushy growth.
For cut flowers, cut the stems above the leaf or bud nodes so the plant will continue to produce more blooms.

FAQ

What happens if you sprinkle zinnia seeds on top of the soil?

If you sprinkle the seeds on top of the soil instead of covering them with 1/4 inch of soil, the seeds will dry out much faster, and the seedlings won't be anchored well in the soil where they absorb water and nutrients.
Do you need to soak zinnia seeds before planting?

No, zinnia seeds don't require soaking before planting.
What month is best for planting zinnia seeds?

The best time depends on whether you plant the seeds directly outdoors or start them indoors. Outdoors, you need to wait until the soil has warmed to at least 70°F. Indoors, the best month is usually around April or May.
Do zinnias grow best in the ground or in pots?

Zinnias grow equally well in the ground and in pots, provided you water them adequately. Like all container plants, they need more water than plants in the garden.