How to Harvest Zinnia Seeds for a Never-Ending Supply of Beautiful Flowers

pink and orange zinnias in garden — Credit:
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Key Points

Saving zinnia seeds lets you grow endless colorful flowers year after year—without spending extra money.
You can collect zinnia seeds when flowers turn brown or while they’re blooming—both ways work well.
To store seeds, let them dry fully, then keep them in a paper envelope or an airtight container in a cool place.
Plant seeds after the last frost, once the soil has warmed and the spring weather is steady.

Zinnias are a true gem of summer, infusing any garden with their vibrant colors and delightful charm. Among the easiest flowers to cultivate, they also serve as stunning cut flowers that can instantly brighten your home. One of the most rewarding aspects of zinnias is the ability to save their seeds, allowing you to enjoy their beauty year after year. With just a single zinnia plant, you can create a never-ending supply of seeds, sparing you the need to purchase them ever again.

Harvesting zinnia seeds is a simple and enjoyable process that even novice gardeners can easily master. Ahead, flower farmers share essential tips on efficiently collecting and storing these beautiful seeds to ensure your summer gardens are filled with zinnias.

Christina Koether, a garden designer and flower farmer at Nomadica, a flower farm in Weston, Connecticut
Mark and Ellen Parlee, owners of Parlee Farms in Tyngsboro, Massachusetts, a family-owned fruit and flower pick-your-own farm in its 38th year

When to Harvest Zinnia Seeds

Zinnia seeds can be harvested when the flower heads have died and turned brown or when the flower is in bloom, says Christina Koether, a garden designer and flower farmer at Nomadica. The method you choose comes down to personal preference, as both are straightforward and rewarding.

Open-Pollinated vs. Hybrid-Pollinated

Understanding the difference between open-pollinated and hybrid varieties is crucial if you intend to save seeds, as one type will produce true-to-parent plants while the other may not.

Open-Pollinated Zinnias

Open-pollinated zinnias are plants pollinated naturally by insects. "The genetics of the seeds, and what those plants will look like, depend entirely on where the bee has been prior to the flower it’s currently visiting," explains Koether. If you have multiple varieties of zinnias growing together, the seeds will be a mix of the genetics of the flowers the bees visited. In contrast, if you only grow one kind of zinnia, and there are no other patches of zinnias nearby, you will likely get seeds that are similar to the parent zinnia plant.

Hybrid-Pollinated Zinnias

Hybrid zinnias are plants produced by crossing two different parent varieties to create specific traits like color, size, or disease resistance, says Koether. "This is where the pollination is controlled, either by hand-pollinating and then covering the flower so pollinators can’t get to it, using something like a gauze drawstring bag, or by using tunnels filled with pollinators to create a controlled pollination environment, she explains. If you only want to save seeds true to the parent zinnia plant, Koether recommends only planting one variety in the garden.

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How to Harvest Zinnia Seeds

Zinnias are some of the easiest flowers to harvest and save seeds from. While the exact number of seeds produced by each zinnia can vary depending on the variety and growing conditions, a single zinnia flower can yield a significant number of seeds, potentially hundreds.

When the Flower Head Has Dried

Koether recommends letting the zinnia flowers bloom on the plant, allowing them to be pollinated and fully mature. "When the flower head looks dead, brown, and crunchy, it’s ready to harvest for seeds."

Gently cut the flower heads off the plant using clean garden shears.
At the base of each petal, you will find a seed. If the seed is firm and plump, it’s fully formed.
Remove any plant material attached to the seeds.
Let the seeds dry completely and store them in a cool, dark place.
Write the zinnia variety and the date it was harvested on the envelope.

When the Flower Is in Bloom

Harvesting zinnia seeds when the flower is in bloom is a simple task. Koether explains that the seeds can easily be retrieved from the outer edge of the outer petals.

Wait until the flower is fully open, which typically occurs a week or two after it first opens.
Gently pull off the outside petals one at a time while the flower is still on the plant, looking for the seeds at the base.
If the seeds are plump and firm, they are suitable for harvesting.
Let the seeds dry completely and store them in a cool, dark place.
Write the zinnia variety and the date it was harvested on the envelope.

"If you have a long growing season and enough time before your first frost, you can plant these seeds the same season," says Koether.

How to Store Zinnia Seeds

Storing zinnia seeds is a very simple process, according to Mark & Ellen Parlee of Parlee Farms in Tyngsboro, Massachusetts. They note that all you need is a sealed container and a cool, dry area to save seeds successfully.

Ensure the seeds are dry: Zinnia seeds must be dry before storing. To ensure all moisture is removed, spread the seeds out evenly over a screen, tray, or paper towel and place them in a cool, well-ventilated, and dry area for a few days to one week until they feel dry and crunchy.
Place the seeds in a paper bag or container: Once your seeds are dry, store them in a paper envelope, paper bag, or airtight container. Paper envelopes and bags are breathable and effective for storage, while an airtight container, such as a glass jar, helps protect the seeds from unwanted moisture. Both storage options are suitable for long-term preservation.
Store in a cool, dry place: Store the container in a cool, dry place, out of direct sunlight, such as a closet, pantry, or basement. Zinnia seeds can remain viable for three to five years when stored properly.

If you choose to use a sealed container, consider adding a food-grade desiccant to absorb any unwanted moisture.

When to Plant Saved Zinnia Seeds

Zinnias thrive in warm soil and will flourish when planted at the appropriate time. Although it might be tempting to sow your seeds as soon as spring arrives, it's important to remember that zinnias require warm soil and weather to thrive.

Plant after the last frost: Zinnias can be directly sown outdoors once the danger of frost has passed, as they are sensitive to cold soil and frost. Consult your local extension office or use your zip code to look up your growing zone to determine your last frost date.
Wait until the soil is warm: The optimal soil temperature for zinnia seed germination ranges from 70 to 80 degrees Fahrenheit. The soil should feel warm to the touch before planting. Zinnias thrive best when daytime temperatures are around 70 degrees Fahrenheit or higher.
Start seeds indoors: If you want to get a jump start on seed sowing, you can sow zinnia seeds indoors 4 to 6 weeks before your last frost date. Once the soil temperatures are warm and the risk of frost has passed, you can transplant your zinnia seedlings outside.