Learn how to grow low-maintenance zinnias and add a long-lasting pop of color to your garden during even the hottest months of the year.
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.
Disclaimer: This post may contain affiliate links. See my disclosure policy for more information.
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.
In the low desert of Arizona:
Start seeds indoors:
Plant seeds or transplants outside:
Zinnias bloom from April to November.
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. Space plants 6” to 18” apart depending on the variety to maximize air circulation and reduce powdery mildew.
2. Plant zinnias in the right location
- Plant zinnias in rich soil amended with compost and organic fertilizer. Zinnias don’t need supplemental fertilizer throughout the season.
- 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.
- I love planting zinnias along the edges or borders of garden beds, where they add beauty and attract pollinators.
3. Cut zinnias back when young for more blooms
This tip for how to grow zinnias will make the biggest difference in the number of blooms. When the young zinnia plant is 18 inches tall, cut the central stem just above 2-3 side shoots. This early pruning encourages multiple stems rather than one.
Flowers to Plant Outside & Seeds to Start Indoors Each Month in the Low Desert of Arizona.
• PLANTING GUIDE: Each month lists annual flowers and bulbs to plant outside & seeds to start indoors.
• BLOOMING GUIDE: Photos show what may be in bloom that month.
4. Harvest flowers often to encourage more blooms
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.
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
At the end of the season, leave the blooms on the largest, prettiest flowers. Let the flower head dry completely on the plant. Seeds are ready when the flower head is dry and brittle. The petals will dry and fall away. The seeds are small and arrow-shaped, look for them in the center of the flower, as you pull out the petals. Read this blog post to learn more about how to save seeds.
Harvest the seeds to plant in your garden next season and share with friends. Teach your friends how to grow zinnias too.
If you enjoyed this post about how to grow zinnias, please share it:
Nehemia Filander
Monday 6th of February 2023
When is the best time or season to plant Zinnias
Angela Judd
Monday 6th of February 2023
They prefer warm soil. Plant a week or two after your last frost.
Teri
Wednesday 3rd of August 2022
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?
Angela Judd
Wednesday 3rd of August 2022
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.
Austin
Saturday 23rd of July 2022
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.
Angela Judd
Friday 29th of July 2022
You could certainly try. They grow and sprout quickly and usually bloom through at least October.
xxx
Tuesday 14th of June 2022
W1e have some zinnias in the school garden.
Xiemna sliva
Tuesday 14th of June 2022
''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,''
Angela Judd
Tuesday 14th of June 2022
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.