Will My Zinnias Reseed Themselves Every Year?

Zinnias are a flowering favorite for many gardeners. But if you are new to zinnias in your garden, you may be wondering if they reseed themselves. In this article, gardening and flower expert Taylor Sievers examines if zinnias drop seeds, or if you'll be replanting them every year on your own.

do zinnias reseed

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In my mind, Summer in the cut flower garden conjures up images of hot, vibrant colors and the feel of rough leaves scratching at my arms as I wade through my waist-deep patch of ‘Benary’s Giant’ zinnias. I love these flowers for their beautiful colors and mostly perfect form.

If you didn’t know this already, Zinnia species are herbaceous annuals native to Mexico. They can range in size from 8 inches to 3 feet tall or more. These hairy-stemmed, rough-leaved relatives of the sunflower have cheerful flowers that come in vibrant colors of red, yellow, orange, pink, purple, white, or mixed colors.

Zinnias are not only beautiful, but they attract pollinators as well. They love full sun and thrive with heat, so they’re a perfect companion flower for your Summer vegetable garden. What makes them even more desirable is how easy they are to grow!

And speaking of zinnias being easy to grow–whether you are a beginning or longtime gardener–I’ll wager you’re always eager to find a beautiful plant that doesn’t require a lot of hands-on maintenance. And a self-seeding plant may be just the ticket! But will zinnias reseed in your backyard garden? Let’s find out!

Will Zinnias Reseed Themselves?

The short answer here is yes. If zinnias are allowed to flower and set seed and the seeds drop to the soil, then there is a good chance that the seeds will germinate and grow the following spring. There is no guarantee that it will happen, but this is one of the main reasons why these flowers are loved by so many gardeners.

Zinnia Growth Requirements

Growth Requirements
These summertime beauties thrive in 70ºF and above.

Overall, zinnias are easy keepers in the garden. Plant the seeds directly into the garden and you’ll be enjoying flowers in as little as 50 to 60 days for some zinnia varieties!

Season

Zinnias are Summer annuals, so that means they typically grow best and flower during warm weather. In fact, zinnias will not grow well if the temperature is below 60ºF. They prefer temperatures of 70ºF and above. Cool, moist conditions of Spring are not ideal for these natives of Mexico. Unfortunately, they will die if they succumb to a hard frost.

Location

Location for Best Growth
Be sure to plant in a nice, sunny spot.

Plant zinnias in full sun. Full sun exposure means that the plants will receive at least 6 to 8 hours of direct sunlight per day. If plants don’t meet their sunlight requirement, they may become stretched and spindly or they may not flower properly.

Soil

Zinnias are not picky about soil type, but they will grow best in a well-draining soil. Most of the time planting in full sun is more important than the perfect soil type. Waterlogged soils that do not often dry out will be a problem because of disease concerns, however. Amending the soil with organic matter, such as compost, will help improve drainage qualities of a heavy clay soil. Also, you can choose to plant zinnias in a raised bed if you feel your site is too swampy.

Moisture

Mulch Around Young Plants
Add mulch around your plants in order to water less often.

Zinnias will become quite drought tolerant once established, but it is important that the plants receive adequate moisture when young. As a general rule of thumb, 1 inch of water per week would be a sufficient amount of water for your zinnias to thrive. In sandy soils, this means you should be watering at least twice a week if there has not been any rainfall. If your soil has higher clay content, once a week should be satisfactory.

Do not water if the soil is wet, but make sure to stick your finger into the soil a few inches down to ensure that it isn’t just the surface that is wet. Water at the base of your plants to reduce incidence of disease. Mulching around your plants will help conserve moisture so you can water less.

Fertilizing Zinnias

Zinnias are moderate feeders. They are one of the easiest flowers to grow in my garden, regardless of whether I fertilize or not. However, it is beneficial to fertilize zinnias with a well-balanced fertilizer either before planting or while the plants are growing. A well-balanced fertilizer has mostly equal parts of the macronutrients nitrogen, phosphorus, and potassium.

You can also choose to amend the soil with a granular fertilizer or with organic components such as compost or manure during your bed preparation.

However, if you are allowing zinnias to reseed, you will likely not be amending the bed much because you will not be turning the soil. You could broadcast fertilizer on top of the soil in the Spring, however, or apply a liquid fertilizer via a watering can or irrigation tape or tubing.

While plants are growing, you can apply a foliar fertilizer to the plants to give them a boost. A foliar fertilizer is a fertilizer that is diluted with water and then sprayed onto the plant leaves for the plant to soak up. A mixture of fish emulsion and seaweed or compost tea is often safe to apply to plants. You can also apply this directly to the soil at the base of the plant.

Make sure that when you are applying foliar fertilizers that you do not spray plants in the heat of the day as this will burn your plants. Many growers like to spray foliar fertilizers in the evening so the plant has enough time to soak up the nutrients and the sun is not directly hitting the leaf surface to cause burning.

Do your research before applying any type of fertilizer to your plants, whether it is labeled “organic” or not.

Thinning

Thinning Your Flowers
Don’t forget to thin out your seedlings to ensure ample space for both growth and reseeding.

It is important to thin out your zinnia seedlings so that there is adequate spacing between each plant. Depending on the variety, you’ll need to make sure plants are thinned to at least 6 to 12 inches apart for small varieties and for large varieties between 9 and 18 inches apart.

Thinning is an important step if you are allowing your zinnias to reseed in the garden. Seeds will often drop in a clump, resulting in several zinnia seedlings emerging at once in the same spot. These plants will not thrive if all are allowed to grow to any size due to space, light, water, and nutrient requirements.

Pinching

Be sure to pinch zinnia seedlings when they are at least 6 to 8 inches tall and have 3 to 4 sets of true leaves. Pinching promotes branching of the main stem, which will increase flower blooms per plant. Pinch the top of the plant off just above a set of leaves.

Deadheading

Deadheading for Growth
Remove all of the dying, faded flowers in order to promote growth of fresh blooms.

It is important to deadhead any dying flower blooms to promote new flowers. In the cut flower world, zinnias are considered “cut-and-come-again” flowers. This means that the more flowers you cut off of the plant, the more the plant will branch and push out new flower blooms. This characteristic is why zinnias are such a beloved Summer flower.

After the flower petals have begun to fade by turning brown or shriveling, you can cut the flower stem off just above a set of leaves. Make sure to cut a little deeper into the plant than just above the first set of leaves. Cut just a few nodes down to keep the plant nicely shaped. Nodes are points where the leaves meet the stem.

Use a pair of clean snippers any time you are pinching, pruning, or deadheading a plant to reduce disease transmission.

Harvesting Zinnias

Harvesting Your Flowers
Be sure to do the “wiggle test” before harvesting to ensure your flowers don’t droop after being cut.

You’ve done it! Your zinnias have successfully made it through a full season, and now you’d like to enjoy these beauties even further.

Zinnias make great cut flowers! They will last in a vase for a week or more if harvested at the correct stage. Make sure that the flowers are fully open before cutting the stems. Also, it is important to perform the “wiggle test”. Gently grip the flower stem about 12 inches down and shake the stem.

If the flower head is floppy, then it’s not time to cut the stem yet. The flower will droop if you cut the stem too early. If you shake the stem and the flower head stays in place, then the stem is ready to cut and be placed in a vase on your table!

Allowing Zinnias to Reseed

Drying to Reseed in Garden
Whether you collect seeds or allow to reseed naturally, you’ll be sure to enjoy bright, fresh blooms every summer.

If you want to collect seeds or allow zinnias to reseed, then you’ll need to let the plant flower and set seed naturally.

This does not mean you can’t enjoy blooms throughout the Summer! Oftentimes gardeners will allow their zinnias to bloom throughout the Summer, and then as Fall approaches they will stop deadheading. The flowers will then fade and dry up.

After the flowers have set seed, you can either leave them alone and hope that the wind and rain will naturally promote seed drop onto the soil surface, or you can push the plant over to “help”.

You will have better germination in the Spring if you crush the seed head in your hands and allow the seeds to drop from your fingers randomly. You can also choose to lightly rake the soil to ensure the seeds will have better seed-to-soil contact.

Or you can be footloose and fancy-free and let nature take its course. It all depends on what kind of gardener you want to be!

Frequently Asked Questions

When will zinnias bloom?

Zinnias are a Summer annual, which means that they will start blooming in early Summer and continue until the first frost in the Fall. There are also many factors involved with blooming, but this is the average duration that you can expect zinnias to bloom.

Sometimes gardeners will plant additional zinnias at later times in order to keep the blooms in their garden at maximum production. This is because a plant over time will gradually slow down with its blooming due to disease or natural energy levels of the plant.

When should you plant zinnias?

Zinnias will not survive a frost, and therefore they should be planted after your last expected frost in the Spring. If you can plant after the temperatures remain 60ºF or above, then you zinnias will be happy! You can plant zinnias all the way up until mid-Summer or at least 60 to 70 days prior to your first expected frost in the Fall.

Can zinnias be started indoors?

Although it can be much easier to allow zinnias to reseed (or to directly sow seed into the garden), you will often have better germination if you start zinnia seed indoors.

This is because you have better control over temperature, light, and moisture compared to seeds exposed to the natural elements. Start zinnia seed inside around 4 to 6 weeks prior to your last estimated frost. Transplant after all danger of frost has passed.

Final Thoughts

Zinnias are beloved annual flowers that bloom early each year. They are easy to grow and also very beautiful. They also attract beneficial birds and insects to the garden. Zinnias also function well as cut flowers, too. On average, zinnias will flower as soon as 60 days after planting, which is wonderful for the eager gardener.

If left alone at the end of the season, they’ll produce hundreds of seeds that will readily reseed in the garden for next year. It’s fun to try out new things in the garden, and allowing plants to self-sow and claim their own territory is an adventure itself!

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