Germinate Zinnia Seeds Indoors: Tips and Tricks For Success

various zinnia seed packets

Starting zinnia flowers from seed is the best way to stock your cut garden with unique varieties of flowers that you can’t find in a garden center or nursery. There are dozens of zinnia varieties in all colors of the rainbow (literally!) and bloom shapes.

With a pack of zinnia seeds, you can fill your garden with flowers for just a few dollars and a little bit of time. Not only will you have beautiful flowers in the summer, but you’ll also get to enjoy their vibrant colors well into the fall.

If starting seeds intimidates you, don’t let it. Many flower seeds, including zinnias, are easy to germinate and grow, so follow these tips and tricks for success, and you’ll be enjoying your homegrown zinnias in no time!

This guide is specific to zinnia seeds, but for a general seed-starting guide, be sure to bookmark this article, Step-By-Step Guide To Starting Seeds Indoors (Plus a sample setup).

A simple method to plant zinnia seeds indoors

A basic setup to start seeds indoors will require just a few supplies.

The two most important supplies will be seed starting mix and lights. It may sound easier to fill a small pot with garden dirt and place it by the window, but that will result in weak seedlings that will struggle all the way to the garden.

Invest in just one bag of seed starting mix (or make your own for cheap!) and one shop light from the hardware store, and your zinnia seeds will grow much better than without them.

Get your seed starting supplies ready

  • Fill your containers with seed-starting mix. You can use a seed tray, small paper cups, peat pots, or even old yogurt containers. Just make sure the container has some drainage holes to let out excess water.
  • The seed starting mix should consist of compost, perlite, and vermiculite, which is light, fluffy, and holds moisture well. Any hardware store or garden center will have bags of pre-made seed starting mix, or make your own for less money. Garden Betty has a great article showing you how to make your own mix with an easy recipe.
  • Make sure the mix is pre-moistened, or mix in some water. The soil should be wet but not saturated. A handful of the mix should form a ball that holds together lightly.
  • Fill your seed trays, cups, or whatever container you are using. Gently press the soil into the container.

Sow the zinnia seeds

  • Grab your zinnia seed packet, and place one seed per tray cell on the soil. If you’re using a container that isn’t divided, then place a seed every 2 inches on the soil surface.
  • Zinnia seeds need to be covered with just 1/4 inch of soil.
  • Mist the soil or water with a gentle stream to settle the seeds and soil in place.
  • You will need to water the seeds regularly until they germinate. If the seeds start sprouting but then dry out, the sprout will die and you’ll need to replant, so don’t forget to keep them moist.
zinnia seeds in the palm of a hand
Zinnia seeds are large and easy to sow. Just remember to cover them with a quarter-inch of soil.

Set up the seed trays under lights

  • Place the seed trays under a row of shop lights, with the light lowered to two inches above the soil. The lights don’t need to be turned on yet, since the ambient light in the room is enough for now.
  • Consider using a heat mat to warm the soil. Zinnias are warm-season flowers and they’ll germinate much quicker in warm soil. If the soil is too cold, the seeds may not germinate at all.
  • Zinnia seeds usually germinate in a week if the soil temperature is 70-75 degrees. Lower temperatures means it will take longer, so if the seeds are in a cooler area, keep that in mind as you’re waiting for the seeds to sprout.
  • Once the seeds have sprouted, they’ll need 16 hours of direct light per day. The easiest way to do this is to put your lights on a timer with the lights on from 6am to 10pm. 

You will need to tend to your seeds every day for the next four or so weeks until they’re ready to transplant to the garden.

During that time, keep the soil moist until the seeds sprout. Adjust the lights, raising them as the plants grow taller as they grow. The lights should be about two inches above the plants to keep the light strong but still give them room to grow. 

You can transplant the zinnia seedlings outside when they’re 3-4 inches tall after all danger of frost has passed. 

Here are some of my favorite practices for easing the transplanting process for my seedlings: 7 Ways To Minimize Transplant Shock In Seedlings.

To get a complete guide on the transplanting process, check out this video from James Prigioni:

Common questions about germinating zinnia seeds

If this is your first year starting zinnias from seed, you might have lingering questions about the process. Let me answer them for you here!

How do you germinate zinnia seeds fast?

Keep the seed trays in warm conditions to speed up the germination time for zinnias. Heat mats and a warm room will make the most significant difference. When the soil is at the optimal temperature for germination (70-75 degrees Fahrenheit), zinnia seeds will sprout in as few as five days.

Should I soak zinnia seeds before planting?

Zinnia seeds don’t need to be soaked before planting. Zinnias are warm-season annual flowers native to hot areas such as Mexico and the southwestern US, so the seeds are programmed to sprout quickly when exposed to water. Once you sow the seeds and water them, that’s enough to trigger germination. 

How long do zinnia seeds take to germinate?

Zinnias generally take 5-10 days to germinate. Seeds sown in trays placed on heat mats to keep the soil warm at 70-75 degrees Fahrenheit will germinate faster, whereas seeds sown in cold soil will take longer, possibly up to three weeks. 

Do zinnia seeds need light to germinate?

Zinnia seeds don’t need light to germinate, and in fact, they should be covered with 1/4 inch of soil when planted. Once the seeds germinate and break the soil’s surface, they will need intense light in the form of a shop light or grow light. 

At what temperature do zinnias germinate?

The ideal temperature to germinate zinnia seeds is 70-75 degrees Fahrenheit. A heat mat placed under the seed trays will bring the soil up to this temperature range. The seeds will still germinate in soil that is cooler than 70 degrees, but it will take longer. 

Do zinnia seeds need cold stratification?

Zinnias do not need cold stratification, which is a process of chilling seeds before planting. Because zinnias are warm-season annuals native to hot regions, the seeds are adapted to germinate without exposure to cold. 

Your turn!

Start with zinnias if you’re looking for an easy way to get into flower gardening. They’re one of the easiest plants to start from seed, and there are so many more varieties available as seeds than what you can buy as a transplant.

All you need is some good-quality seed starting mix, lights, and seeds. Just be sure to keep the seeds warm and moist to get them to germinate quickly.

So why not give it a try? Starting your own flowers from seeds is a great way to start gardening, and you might be surprised at how much fun it can be.

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