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January 16th 2024

How to Grow Zinnias

Written by
Floret

Zinnias are one of the easiest cut flowers to grow. They are the perfect first crop for beginning gardeners and are reliable, prolific producers no matter where you garden. 

In addition to churning out buckets and buckets of beautiful, long-stemmed blooms that are perfect for cutting, they are well-loved by pollinators. 

Zinnias resent cold weather and prefer to be planted after things have warmed up a bit. 

Many gardeners in warmer parts of the world are able to successfully direct-seed zinnias straight into the garden, but here in cool Washington we start our plants early in the greenhouse, 4 to 6 weeks before our last spring frost. 

Plants are then tucked into the field once the weather has sufficiently warmed and all danger of frost has passed.

Like every flower grown on our farm, we try to give them the best start possible and prepare our planting beds with a generous dose of compost and organic fertilizer. Learn more about soil preparation here.

Once planting beds are prepared, we lay down drip irrigation lines and then cover the beds with a layer of preburned landscape fabric. Using fabric is not necessary for success, but here on the farm, we use it to increase heat and suppress weeds.

Plants are spaced 9 to 12 in (23 to 30 cm) apart and watered deeply one to two times per week depending on the weather. If given good soil and a steady supply of water, plants can get huge and will require some type of support. 

If grown in long rows, plants can be corralled by pounding heavy stakes or T-posts around the perimeter of the bed and using bailing twine to create a string-lined box to hold the plants upright. If you’re growing zinnias in your garden beds, individual plants can be tied to stakes with twine. 

The secret to getting the most abundant flower production and longest stems from your zinnias is pinching them when they are young. When plants are 8 to 12 in (20 to 30 cm) tall, take sharp pruners and snip the top 3 to 4 in (7 to 10 cm) off the plant, just above a set of leaves. This signals the plant to send up multiple stems from below where the cut was made. 

During spells of hot, dry weather, zinnias are prone to powdery mildew. Providing good airflow around the plants and making sure that they aren’t experiencing any drought stress will help minimize disease pressure. 

We’ve found that preventatively spraying a mixture of Cease and MilStop (both organic fungicides) every 7 to 10 days keeps it at bay. 

If you’re not regularly harvesting your zinnias, be sure to deadhead any spent blooms to help focus the plant’s energy on producing new flowers and not going to seed.

Zinnias need to be picked when they are fully ripe or they won’t last in the vase. To tell whether a zinnia is ready to harvest, use the “wiggle test.” Simply grab the stem about 8 in (20 cm) down from the flower head and gently shake it. If the stem is droopy or bends, it is not ready to cut. If the stem is stiff and remains erect, it is ready to harvest. 

Zinnias are considered a “dirty” flower and benefit from a drop or two of bleach in their water. Flowers are very cold sensitive, so don’t put them in the cooler. If floral preservative is added to the water, zinnias should last about a week in the vase.

I’ve been growing zinnias since the very beginning, and every year I fall more and more in love with them. If you want to see all of my favorite varieties, check out the zinnia section of the Floret Library. 

I would love to hear about your experience with this wonderful group of plants. Do you grow zinnias or plan to add them to your garden this coming season? If so, what are your favorite varieties, or what new treasures are you adding to your wish list?


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12 Comments

  1. Jennifer Wolcott on

    My Granddaughter is getting married next September and asked me to do the flowers. She chose Zinnies and I now have 16 packages of seeds. There are so many! I’m planning to start them myself and then stick them all over. (I have been gardening for about 60 years so I do know what I’m getting into.)

    Reply
  2. Nina on

    I would love to learn how to save seeds from zinnias. Please make a video how to so we can continue growing these beautiful flowers !!!!

    Reply
  3. Allison on

    I live in a beautiful part of the world, Hout Bay, Cape Town and have just grown Zinnias for the first time ever…I’m hooked. I have lots of brightly coloured zinnias in amongst my dahlias and they just make me so happy when I see them every morning. They also seem to be quite robust and have coped very well with our nasty Summer wind which is known as the Cape South Easter. It blows, sometimes gale force, and whilst I am hugging my dahlias, tying up and staking them, the Zinnias seem to be fine. What I wouldn’t do to get my hands on some Alpenglow, Precious metals and Unicorn Mix. I wake up dreaming about them. I’m holding thumbs that the shipping might work out for this part of the world.

    Thank you Erin and team for the inspiration.
    Allison x

    Reply
  4. melanie perrone on

    I grow hundreds of purple zinnias in my front yard flower bed every year. last year I was fortunate when even though I didn’t plant them in the spring, they self seeded and had quite a bit of zinnias growing in the bed. this year I look forward to adding a few new varieties of zinnias, along with all the other seeds that the pollinators love.

    Reply
  5. melly on

    My Michigan mother in law would scatter zinnia seeds in the wind come springtime and always had the loveliest blooms alongside her barn. I’ve found them easy to grow in my zone 5 garden too. I’m so excited for your new venture. Congratulations, Floret!

    Reply
  6. Valerie Pagounis on

    I am in zone 6B and have had great luck growing Zinnias for years . I have started seeds indoors & outside using the winter sowing method. I have loved your Oklahoma, Carmines, & Benary’s. I fill my border in the front yard against the fence & all around my raised vegetable garden beds. I can not wait until Feb 6th for all of your Floret everything ! ! I’ve set reminders in my phone, on the wall calendar in the kitchen, a post it note on my computer & one of my daughter’s also set a reminder on her phone, too! We just finished watching your video on You Tube. Thank You for all you do and you have inspired me to start saving seeds this year :)

    Reply
  7. Christy Foster on

    I absolutely love zinnias but have had such a hard time here with brown spot. No matter where on our farm I have tried growing them the brown spot gets them by late August.

    Reply
  8. Jennifer Sevin on

    What type of flower is next to the zinnias in the last picture? Is that a bottle brush hydrangea?

    Reply
  9. Connie Tibbits on

    I have good luck growing zinnias in Wisconsin. I start zinnia seeds indoors and outside to get a longer growing season.

    Reply
  10. Jennifer on

    I’ve had such success with zinnias here in hot, sunny central California. I love the Benary giants, state fair, several of the Oklahomas, and Queen lime red. I also love to save seeds and grow them out again. I’m looking forward to trying some of the new Florets!

    Reply
  11. Maxine on

    New to flower garden, but excited to get started this year. I’m looking at the new lime queen series. I have had a few California giants in my yard for a couple of years and just fell in love with them. Thank you for the inspiration and information. Max Griffith

    Reply

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