How to grow Zinnias – 5 Tips for Growing Zinnias
Learn how to grow low-maintenance zinnias and add a long-lasting pop of color to your garden during even the hottest months.
Butterflies, bees, hummingbirds, and other pollinators are drawn to these vibrant flowers. Zinnias make excellent cut flowers and come in varied sizes, colors, and textures.
5 Tips for How to Grow Zinnias
1. Start zinnia seeds indoors or in the garden
If you have purchased zinnias from a local nursery and been disappointed with the results, try planting them from seed instead. I use zinnia seeds from Botanical Interests.
I’ve had the most success starting zinnias indoors in seed trays just a few weeks before the last frost date. I use these seed starting trays from Bootstrap Farmer. I transplant them into the garden when they are a few inches tall.
The best time to plant zinnias is in late spring after the last frost has passed and the soil has warmed up. Typically, this is around late April to early May in most regions, but it may vary depending on your local climate. Zinnias thrive in warm weather and full sun, so planting them at the right time ensures they grow strong and produce vibrant blooms throughout the summer.
In the low desert of Arizona:
- Start seeds indoors:
- February – May
- Plant seeds or transplants outside:
- March – June
- Zinnias bloom from April to November.
Because they grow well in similar conditions, gomphrena is an excellent companion plant for zinnias. Learn how to grow gomphrena in this guide.
To start zinnias from seed (indoors or outside), poke the pointy end of the seed into the soil and then cover it lightly with soil.
Sow zinnia seeds about 1/4-inch deep and space them 6-12 inches apart, depending on the variety. For larger varieties, allow 12-18 inches between plants. This will ensure proper air circulation and reduce the risk of diseases.
2. Care for zinnias as they grow
Plant zinnias in rich soil amended with compost and organic fertilizer. Choose well-draining soil with a pH between 6.0 and 7.0. Amend the soil with compost or aged manure to improve fertility and drainage if needed. Zinnias don’t need supplemental fertilizer throughout the season.
I love planting zinnias along the edges or borders of garden beds, where they add beauty and attract pollinators.
Zinnias not only brighten the garden but attract pollinators to help cucumbers thrive. See more companion options in this post on growing cucumbers with flowers and herbs.
Give zinnias plenty of sun. Zinnias grown in the shade are often leggy and susceptible to mildew.
Zinnias do not like getting their leaves wet. Use drip irrigation rather than spraying them overhead. Water can cause problems with powdery mildew. Zinnias prefer consistent moisture but don’t like to be over-watered. Water them deeply once or twice a week, depending on your local climate. Avoid overhead watering to prevent leaf diseases.
Taller zinnia varieties may require staking or support to prevent them from toppling over in heavy rain or wind.
Watch for pests such as aphids, spider mites, and caterpillars. Treat any infestations with organic solutions. To prevent fungal diseases like powdery mildew, ensure proper spacing and avoid overhead watering.
3. Cut zinnias back when young for more blooms
I recommend cutting back zinnia seedlings to encourage more blooms and create bushier plants. For most zinnia varieties, start pruning when the seedlings are about 6-8 inches tall. Use clean, sharp pruning shears or scissors to make the cuts.
To properly prune zinnia seedlings, pinch or cut off the top 1-2 inches of the main stem just above a leaf node or set of leaves. This will stimulate side branching and result in a bushier plant with more flowers. Make sure to remove any weak or leggy growth, leaving only strong and healthy stems.
Prune your zinnias periodically throughout the growing season to maintain their shape and maximize blooming potential.
The Perpetual Annual Flower Planting Calendar, available in my shop, helps you learn when to plant flowers in the low desert of Arizona and whether to plant seeds or transplants.
4. Harvest flowers often to encourage more blooms
Cut zinnia flowers in the morning when they are fully open for the longest vase life. Zinnia blooms don’t continue to open once cut. Harvest flowers when the petals are open and the stem has stiffened. Zinnias are an excellent cut flower and last up to 10 days in a vase with a floral preservative. Change the water in the vase every couple of days to keep them looking fresh.
If you are not harvesting the blooms for cut flowers, keep the spent flowers deadheaded to encourage the plant to produce new blooms (not seeds).
5. Save zinnia seeds each season
To save and store zinnia seeds for future planting:
- Begin by allowing a few of your healthiest blooms to mature fully and dry out on the plant.
- Once the flower heads turn brown and become brittle, carefully snip them off with clean, sharp scissors or pruning shears.
- Bring the flower heads indoors and place them in a well-ventilated area to continue drying for a week or two.
- When fully dry, gently break apart the flower head, revealing the arrowhead-shaped seeds attached to the base of each petal. Separate the seeds from debris and allow them to air-dry for another day or two.
- Store the seeds in a labeled paper envelope or small glass jar, ensuring they are completely dry before sealing. Keep the container in a cool, dark, and dry location, such as a cupboard or closet, until you’re ready to plant the seeds in the next growing season.
This method preserves the genetic diversity of your zinnias and allows you to enjoy their vibrant blooms year after year. Read this blog post to learn more about how to save seeds. Learn how to grow strawflowers in this guide.
Hi! I planted Zinnia from seed at the end of May, and so far I have 6″ skinny stems with only a few leaves. The bottom leaves keep turning brown and falling off. I’m watering daily at sunrise and I have them mulched with a shade cloth, but is the AZ sun still too hot for them?
Hi. That is frustrating. What is your soil like? Mine are in full sun with about 15 inches of good soil. Be sure not to get water on the leaves. Also cut them back when they are a few inches tall to encourage branching stems.
My zinnias have tiny blooms. I did not read your post until now. Is it too late to prune them?
They are beautiful plants. Just disappointed in blooms.
You can always cut back to above two sets of leaves. However, the size of the bloom is determined by which variety you planted, not necessarily if you pinched them back or not.
On friday me and my class harvested zinnias and then we took them home to have zinnias at our homes.
Last Friday we got zinnias in packets and we learned more about this plant and am excited for them to grow. Your vlog showed me more things to see in plants and i know about zinnias now. I love the facts about zinnias and how much can be grown by a zinnia. It also keeps people entertained if they have nothing to do. We also have some zinnias in the school garden that are doing amazing with the water and sun, soil.
Hello! At my summer school we made seed packets with zinnias in them.I also have a question for you, can zinnias survive with a lot more plants around them?
Zinnias can be planted near other plants.
Hi, All your information about Zinnias are amazing .But how does the soil have to be and how much water do you have to put so i don’t overwater them and how many months does it need so the seeds sprout?
Zinnias like soil with compost. Seeds sprout in just a few days. Water when the soil dries out a little.
Me and the rest of the class harvested Zinnias. The popcorn was good because we also got popcorn that day.
I have lots of questions ‘but all i want to know is why zinnias are made why do they exist could zinnias be helpful and healthy is it safe can we water twice a day or a week
The bees and butterflies love zinnias. Water when the soil dries out a bit.
@Angela Judd,
Bees and butterflies love zinnias that are open in the center so the insects can get at the nectar. Some zinnia varieties have so many petals that insects can’t get at the nectar.
Small, narrow-leaved zinnias make pretty dry flowers. The common garden zinnia or Zinnia Elegans is also called “Youth-and-age
”HI, I have a Zinnia but not much about them yet” like what kind of soil, the teampercher tw0,I wondered if there’s a limit of where it stops growing?.And do you know why they turn brown and the leafs two do we put more watar or does it need food,”
Zinnias like warm weather, so they will stop growing when it gets cold. The leaves don’t like to get wet when you water (unless its rain) maybe that is why.
W1e have some zinnias in the school garden.
Is it safe to plant zinnia seeds in late July-early August here in Mesa? Everything in my garden bed has burned up on me. The zinnias grew great until mid-June when it hit 110.
You could certainly try. They grow and sprout quickly and usually bloom through at least October.
I am pretty sure I planted way too many seeds and my zinnias are just starting to bloom. The flowers are teeny tiny. I have read that I should have thinned them out when they were sprouting to prevent overcrowding (resulting in tiny flowers). Is it too late to thin them now?
It’s always better to thin earlier, but it’s not too late thin them now. I would cut them at the base, rather than pulling them up to thin them. Flower size can also be determined by the variety you are growing.
When is the best time or season to plant Zinnias
They prefer warm soil. Plant a week or two after your last frost.
my zinnia stems are growing but the bottom of the stem is browm so
I cut it baxk to the green in the stem
If I put the pruned trimmings in a glass of water, will they root and eventually be able to plant again? Or should I just throw the pruned trimmings away?
Good question, I’m not sure. If you try it, let me know.
Thank u for this arrival. I learned a lot about zinnias.
Thank you for your detailed instructions and photos, especially where to cut the stem to stimulate side growth. This is one of the most helpful articles I’ve found on growing zinnias.
Glad it was helpful.
When do you cut back petunias and how far?
Mulch in winter?
Are you asking about zinnias? Zinnias are an annual and will need to be replanted next spring.