Skip to content

How To Plant Zinnia Seeds: From Starting Seeds Indoors To Harvesting

  • Amy 

How To Plant Zinnia Seeds 

Growing zinnia plants from seed indoors is a great way to get started with gardening. It’s also a fun project for kids who love flowers. But growing zinnias from seed takes patience and skill.

In this article, I’ll teach you how to grow zinnia seeds indoors without soil. 

I’ll walk you through the whole process step-by-step.

Don’t worry; it’s not as complicated as it sounds.

You’ll learn everything you need to know to grow beautiful zinnias flowers from seed inside your home up to harvesting.

What To Prepare

  • Zinnia seeds
  • Seed starting containers (cell tray or small pots)
  • Seed starting medium (seed compost and some Vermiculite)
  • A container for bottom watering
  • A heat mat
  • Shelving
  • Grow lights, or a good light source (fourteen to sixteen hours of light daily)

Planting Process

  • Fill your container of choice with your seed starting medium. Tap the seed tray a bit on a hard surface to set them and remove gaps and air pockets.
  • You can moisten the medium before adding them or bottom water them after planting – either is fine. 
  • Plant one or two seeds per container or cell if using a cell tray. Make a little indention on the soil surface, then poke the pointy end of the seed into the medium. Cover that with vermiculite.
  • Water thoroughly.

If you have a spot in your house where you get sunlight at least fourteen to sixteen hours per day, then go ahead and place your container there.

If you don’t have one, you can grow them under lights. 

You can also utilize bottom heat from a heat mat to germinate the seedlings. They provide consistent warm soil temperature that helps the seedlings grow. 

How To Use A Bottom Heat/ Heat Mat

After watering thoroughly, place your container on top of a heat mat. 

We use bottom water for this method to keep the soil moist at all times. Moist soil conditions are especially important if you’re using a heat mat because it can dry out the medium. Dry soil is bad for the germinating process. So it’s important to keep an eye on your plant. Keep a bucket of water or a glass of water near them so you can remember to give them some.

Turn off the heat mats every night as you turn off our grow lights. Turn them back on again in the morning.

Once the seedlings sprout, turn off the heat mat and place the plants under the grow lights.

How To Use Grow Lights For Your Zinnia

Zinnias grown in the shade are often leggy. They need at least fourteen to sixteen hours of light every day to thrive. 

Keep your zinnias under grow lights until they can be repotted. Make sure to harden off or acclimate your plants to the place you’ll be transferring them to so they don’t get stressed. 

Planting Zinnia Seedling Plants Into The Garden

  • When your zinnias have formed two pairs of leaves, you can now pick out the seedlings. 
  • Harden the starter plants off first before planting them in your garden. Ensure that there is no risk of frost before transferring them.
  • You can just place them in your average, well-drained garden soil, or you can make soil amendments as needed. 
  • Space plants by panting them 30cm apart in your garden. Make sure to place them where they can get plenty of sunlight.
  • Maintain soil moisture for a while. Keep the soil well watered while the seedlings are still getting established. Only water as necessary after that. 

Tip In Growing Zinnias

  • Place supports

Once the zinnias grow, they will be tall plants and have a top-heavy plant crown. Use stakes to support them and prevent them from getting toppled over by the wind.

Place the supports while the plants are young so they can grow into them.

If you put them when they’re mature, you may damage the plant while trying to fix them into the correct position.

  • Practice pruning

When the young zinnias grow to around 6-8 inches tall, start pruning. This will make a big difference in the number of blooms you’ll get. 

To prune, cut the central stem just above 2-3 side shoots.

  • Deadhead your zinnia

Deadheading is basically removing any dead or dying flowers to make way for a new one. 

To deadhead, snip just above the next leaves down the stem of the flower. 

  • Practice pinching

Pinching is a simple pruning method where you literally just pinch off some stem tips. The pinching process causes the plant to grow additional stems, and that means you’ll get more flowers and make the most out of your beautiful plants.

When To Harvest Zinnias

Harvest your zinnias when they have lots of long stems and good sized flowers. Do the wiggle test to check the bloom maturity.

To test maturity, place two fingers approximately two to three inches on the stem below the flower and wiggle it.

If the flower stays stiff and upright and doesn’t bend while you wiggle it back and forth, it is a mature bloom and is ready to be harvested.

If it sways and bends, it’s still an immature bloom. 

Do this per individual blooms.

Harvesting Zinnias

After passing the wiggle test, you can now harvest your zinnias.

Cut deep and at an angle. Remember to remove any leaves and side shoots on the cut stem and only leave the top two leaves. 

Make sure none of that is below the water in your container.

Make sure to harvest them when it’s dry and do it in the cooler hours of the day. Immediately place the cut stem directly into water or holding solution after cutting. 

Allow the stems to soak up the water in a shaded place.

Change water as necessary

Do Zinnias Grow Back After Cutting?

Yes! Zinnias bloom all summer long, and new stems will grow after you harvest. In fact, you can even root plants from the stem cutting of your zinnia to propagate them!

Can You Grow Zinnias As A Houseplant? 

If your house gets fourteen to sixteen hours of light every day, then yes. If not, then your zinnia may not perform well in your house.

Zinnias require full sun and hot temperatures to grow well.

Final Words

In conclusion, planting zinnias from seed is easier than you might think.

All you have to do is plant seeds indoors, wait until they sprout, and transplant them into the garden when the weather gets warmer. Just make sure they get plenty of light and constant moisture.

And if you’d like to add even more colour to your yard, consider growing different colours of zinnias together. They look stunning when mixed together.

 See you in another article!

Join the conversation

Your email address will not be published.

nv-author-image

Amy Toliver

Hey'all I'm Amy, a born foodie and diagnosed with celiac disease 7 years ago. I refused to cave into tasteless, boring gulten free food and create my own! On my blog you'll find info & cool facts along with recipes, all on gluten free foods!