How to Plant Zinnia Seeds

Updated on 06/06/22

Reviewed by

items for planting zinnia seeds — The Spruce / Candace Madonna

Project Overview

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, you can 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 fun 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 warmed to 70-plus degrees Fahrenheit 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.

Equipment / Tools

Hand trowel
Hand transplanter
Garden shears

Materials

Zinnia seeds
Seed starting mix
Peat pots
Compost

Sow Seeds Outdoors

The easiest way to start zinnias is to plant them directly in their final beds outdoors. It takes air and soil of more than 70 degrees Fahrenheit 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 air can flow 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, you can 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, on the other hand, will risk one of the only diseases zinnias are susceptible to: powdery mildew. Keep water to about an inch a week, from all sources. 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 can 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, you can remove it and plant something else in its place. For heirloom varieties, let a few go to seed and be sure to collect them for 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