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The 5 Zinnia Growth Stages

When the weather finally warms and we start to see summer on the horizon, we’re also likely to spot fluffy, colorful blooms both in our neighbor’s garden and at our local nursery shops. Zinnias are beloved for their effortless cultivation and reliable bloom season, which makes them the perfect choice for first-time gardeners. 

Their one downside is being annual plants. That means that they only bloom for one season before dying. That’s why it’s important to understand the five zinnia growth stages so that you can best take advantage of your zinnia’s short life cycle. 

Zinnia growth stages

Keep reading to discover the zinnia growth stages, and how to care for your flowers in each stage!

Planting Zinnia

Zinnia blooms

Before we get into the zinnia growth stages, let’s take a look at the step that must happen before the rest of them follow: planting zinnias. After all, growth can’t happen without planting first!

As with most plants, you can choose to either start from seed, or from young transplants. If you start from seed, you can plant them indoors and transplant them outdoors after the last frost. If you’d rather use transplants, you can simply wait to buy them until the last frost has passed, and then plant them directly into your garden. 

Whatever you choose to do, remember that zinnias love warmth. They are not cold resistant, so it is very important to leave a good amount of wiggle room around the last frost date. Don’t take any unnecessary risks!

The soil required to accompany your plant through the zinnia growth stages is pretty standard. You should use a rich, high-quality potting mix with good drainage. One of the worst things you can do is let the soil get soggy: this could rot the seeds or roots before the zinnia even has a chance to flower!

If you’re starting from seed, plant them about a fourth of an inch into the soil, and water them frequently enough to keep the soil moist. Later in the zinnia growth stages, the plant will be more drought resistant, but not now.

Check the seed packet for specific guidelines on spacing. You don’t want the young plants to grow so close together that it prevents air circulation! If you bought transplants from your local nursery, ask the staff how much space you should give your plants. 

Five Zinnia Growth Stages

Zinnia seeds

1. Germination

A zinnia’s lifecycle officially begins with germination, which is the first of the five zinnia growth stages. Germination is when the shell of the little seed splits open, and the roots push through and start to take hold. This usually happens a little over a week after they’re planted. 

Germination typically happens when the soil is between 69 and 76 degrees Fahrenheit. As I’ve mentioned, zinnias are warmth-loving plants! If it’s any colder than that, then you risk the seed dying before germination can start. 

Make sure to keep the soil damp throughout this step in the zinnia growth stage. Sometimes, watering washes away the soil’s nutrients, so you could also consider adding fertilizer to the soil to prevent this from happening.

2. Growth

The next step in the zinnia growth stages is—you guessed it—growth! To continue past its germination phase, your zinnia sprout will need a continued six to eight hours of full sun. 

If you are growing your zinnia from seed indoors and in containers, now is the time to transfer them into your garden, or into larger pots. The plants should be at least six inches tall, and the threat of the last frost should be long gone. 

Transplanting them outdoors or into a bigger bot is important during the growth phase, because it allows their roots to develop more strongly. As you might imagine, their new location must still be able to receive full sunlight for six to eight hours a day. 

3. Flowering

The next step in the zinnia growth stage is my personal favorite. It’s time to reap the rewards of all your hard work by enjoying their beautiful colors in your home or backyard. 

Flowering, which is the third step in the zinnia growth stage, usually takes place from mid-summer until the fall. Zinnias grow one flower at the top of each stem, and they can bloom in a myriad of different colors, including white, pink, red, and even multi-colored!

Zinnia flowerheads can range in size from one to seven inches in diameter. Those are big flowers! Like daisies, the blooms can also develop one or more rows of petals, which themselves can grow in various shapes and curvatures. 

The amazing thing about zinnias is that they are well known for their very long blooming period. They can bloom continuously for several weeks, and sometimes even for up to five months! Talk about sustained colors in your garden. 

To help in this zinnia growth stage and prolong the flowering, I suggest you include a liquid fertilizer solution in your biweekly maintenance routine. You should also practice deadheading, which encourages your zinnia plant to continue flowering instead of producing new seeds. 

As the flowering stage comes to an end and the flowers begin to wilt, you can begin to water less frequently, but don’t let the soil become dry. 

4. Pollination

The second to last step in the zinnia growth stage is pollination. The purpose of pollination in nature is to allow plants to successfully grow fruit and/or seeds for reproduction. 

Zinnia plants are special because, having both stamens and pistons, they can self-pollinate. But nature usually lends a hand with the help of pollinators like bees, butterflies, and hummingbirds, too. 

In fact, zinnias are known for attracting pollinators, which is another reason why gardeners love them. They help ensure that other plants in their vicinity (who don’t have the ability to self-pollinate!) also get some pollinator attention!

5. Seed Retrieval

Last but not least in the zinnia growth stages, we have the seed retrieval. The step isn’t obligatory, but how great would it be to harvest your own seeds to replant next season? It saves you money, and reconnects you to nature in a way that is usually blocked by modern life.

Before collecting the seeds, you need to allow your zinnia flowers to dry out completely before cutting them from the zinnia plant. If you pick them too soon, the seeds might not be mature enough to germinate when planted. 

So how do you know when a flower is dry enough? Your zinnia bloom is completely dry when it feels brittle and has turned completely brown. At that point you can take the flower head, remove the dried petals, and tape it gently to release the seeds. If that doesn’t do it, you can also rub it gently between your fingers.

Catch the seeds on a napkin or paper plate, then transfer them onto a mesh screen to make sure they are completely dry on all sides. Then you can store them until the next planting season comes around! 

Where to Buy Zinnia Seeds and Transplants

Zinnia bloom

Luckily for us, zinnias are popular flowers, so it’s easy to find both seeds and young transplants to kickstart your own zinnia growth stages. 

You can visit your local nursery, where the staff will be able to help you determine the right time of the year to plant and transplant your zinnia flowers. They’ll also be able to advise you on companion plants to grow alongside them to make for a beautifully diverse garden. 

If you don’t have the time for a trip to the nursery, however, there are lots of options online, too! In fact, I suggest you buy your zinnias online from reputable sources to avoid the hassle of in-person shopping. My favorite option is Nature Hills!

Tips to Growing Zinnias

Zinnia flowers

Now that we’ve covered the five zinnia growth stages, let me give you some more tips and tricks to ensure a successful lifecycle for this beautiful plant.

  • Whether you’re planting seeds or transplants into your outdoor garden, clear the soil of weeds before you get started. They could harm your zinnia plant’s future growth if they stick around. 
  • Plant your seeds or transplants outdoors on a day without wind. 
  • Zinnias can easily be damaged during the transplanting process. If you’re starting from seed indoors, consider planting them in decomposable containers that you can put straight into the earth or a bigger pot when the time is right. 
  • Use drip irrigation to water your zinnia plants. Any other watering system that gets their leaves wet can eventually lead to mold or powdery mildew. 
  • Pruning the central stem to just a little higher than the side shoots when the plant is still young will help your zinnia grow many stems, and encourage a fuller bloom. 
  • Zinnias are susceptible to pests like aphids, whiteflies, and more. Prevention is always the best solution, but if you arrive at the problem too late, treat it with an organic pesticide. 
  • Zinnias are also susceptible to fungal diseases like powdery mildew and Alternaria leaf spot. As with pests, the best solution is prevention. Prevention means growing your zinnia plants with plenty of sunlight, air circulation, and watering them in the morning so that there is no potential for mold to form during the night. Remember to also get rid of weeds and dead leaves or flowers. If that doesn’t work, talk with the experts at your local nursery for advice. 

Fun Facts About Zinnias

Zinnia flowers

Still can’t get enough of these beautiful flowers? Here is some more information about how special they are!

  • NASA uses Zinnia plants for agricultural experiments both on earth and at the International Space Station. That means zinnias are playing a role in the development of sustainable agricultural practices for future long-term space missions—like traveling to Mars!
  • Zinnias are native to Mexico.
  • Because zinnia flowers have strong, erect stems and big flowerheads, they’re great to use in bouquets and flower arrangements. They can last up to 10 days in a vase!
  • Zinnias come in virtually every color except for true blue. In bouquets, they look great next to petunias, marigolds, and dahlias. 
  • Once you pick a zinnia flower from the plant, the flower doesn’t continue to bloom. That means you have to wait until the flower has opened completely before cutting it for your bouquet!
  • Zinnias are the perfect addition to cottagecore, boho, and farmhouse decor.
  • Zinnias come in many different varieties. That means there’s certainly a zinnia variety out there that is perfect for your garden, no matter what plants you’re already growing there. For example, you can buy giant zinnias (they grow up to four feet tall!) as well as dwarf zinnias, whose growth may stay under a single foot.

Now You Know All About the Growth of Zinnias!

Easy to grow, drought-resistance (once established), colorful, and self-pollinating—what else could you want from a plant? There’s a reason why zinnias are so popular. Beginner gardeners can master the zinnia growth stages with ease, and veteran gardeners return to the routine with familiarity and satisfaction. 

Excited to continue your flower-growing adventures? If you appreciated the information here, start thinking about companion plants for your zinnias and check out our daisy flower page for guides on planting, growing, caring, harvesting, and more!

Interested in more zinnia content? Visit my zinnia page for more growing tips, care guides, bouquet suggestions, and more!