9 Tips For Growing Zinnias In Pots

Zinnias are gorgeous annuals with a lot to offer in the looks department. After seeing these plants year after year in large gardens, I started to wonder. Can you grow zinnias in pots?

Yes, you can grow zinnia in pots that are 8 to 10 inches deep. You can pick compact varieties that look great and don’t take much space. You need to grow zinnias in warm weather and provide at least 6 hours direct sunlight. Plant seeds or seedlings in the pot and provide sufficient water.

I’ve written a lot more details of each of these steps that can help you if you’re looking to grow some zinnias in your own container garden.

1. Pick the best time to grow zinnias

The zinnia plant is one of the easiest annual flowers to grow. But, your success will depend heavily on timing. These plants complete their entire growth cycle within a year. So, starting early is a must.

You have a couple of options here. If you want to get started as early as possible, you can germinate seeds indoors. With this route, you want to start sowing about 6 weeks before the last spring frost. This will give your plants plenty of time to develop before moving outside.

I recommend that you start seeds indoors because it increases the germination rate. You can take better care of the zinnia seedlings and ensure they grow healthy before transplant.

Now, if you’d rather plant directly outside, you have to wait a bit longer. However, choosing to wait may be better. Zinnias can be a bit finicky about transplantations. This is especially true if you’re moving them from the warmth of your house to the cool outdoors.

To plant outside, you must wait until all threats of frost are over. These plants can grow when temperatures are around 60 degrees Fahrenheit. But, they do best when daytime temperatures are around 74 to 84 degrees.

Where Can Zinnias Grow?

Zinnias are quite hardy despite the delicate flowers they produce. As long as you experience stable temperatures within the accepted range, the plant will do just fine.

Zinnias thrive in hardiness zones 3 through 10.

2. Find out how long zinnias take to grow

Zinnias don’t take long at all to reach maturity. Whether you plant from seed or young seedlings, you’ll experience rapid growth once the weather warms up.

On average, it takes about 60 days for the plant to start blooming.

When Do Zinnias Bloom?

The cool thing about zinnias is that they have a long bloom cycle. Once they reach maturity, these plants will continue to bloom until the weather prevents them from producing any more flowers. Depending on your location, this could be anywhere from several weeks to several months.

Usually, gardeners will start to see those gorgeous flowers appear in the late spring. As flowers die off, new ones will appear until the first frost of fall.

What Varieties Are Best?

There’s no shortage of cultivars to choose from. Zinnias come in a range of beautiful colors. Not only that, but there are a few different types that vary based on the petal arrangement.

Those parameters aren’t going to have a huge effect on the growth of the plant in a pot. But, its height will.

Shorter varieties perform best in containers. They don’t spread out as far as taller varieties, making it easy for the pot to support its needs. Plus, shorter zinnias can grow quicker and start producing flowers much sooner.

Read this post if you want to grow zinnias in containers but have a limited budget. You can get a lot of the materials for free or cheap when growing plants

Some popular short zinnia cultivars include Zahara, Solcito, and the Raspberry Lemonade Mix.

You can also opt for dwarf varieties, such as Small World, Dasher, and Thumbelina. Those plants usually only get to be about 6 inches tall.

3. Choose the right pot to grow zinnias

The key to successfully growing zinnia is to choose the right container. Luckily, that’s not too difficult. These plants are quite adaptable and thrive in a wide variety of containers.

Size

The first thing to consider is the zinnia pot size. The spread of the roots and foliage all depend on the cultivar. But, you can expect your plant to be about one to one and a half feet wide when fully grown.

Compared to other plants, this isn’t very big at all.

How many zinnias per pot?

You can grow one zinnia plant in an 8 to 10 inch pot. You can grow two plants in a 12 to 14 inch pot. And you can grow up to three plants in a 14 to 16 inch pot.

You can grow zinnias as well in pots as in the ground as suggested by experts. But you need to provide them with the required nutrients, sunlight, and moisture.

Material and Design

Zinnias aren’t picky about materials. They grow well in any kind of container as long as it has enough room to support its growth. You can choose cost-effective plastic pots, fancier ceramic pots, or even recycled wood containers.

These plants also do very well in hanging baskets or window sill planters.

Just make sure that the container you choose has at least 8 inches of width to accommodate the plant.

I like ceramic pots to grow plants because they absorb moisture and help prevent the problem of overwatering.

4. Prepare the pot for planting zinnias

Some additional prep work is important if you want your plant to reach its full potential. There are a couple of steps you can take to ensure that the pot is ready for planting.

Sterilization

Here’s something that many gardeners don’t remember to do. If you’re using a recycled container that previously housed another plant, you need to sterilize it. Even brand-new pots may require sterilization if kept around other plants.

Pots can easily spread diseases and fungal spores. The last thing you want is your precious flower plant to suffer from disease before it blooms, right?

To sterilize the pot, soak it in diluted bleach. Mix the bleach with water so that only 10 percent of the solution is bleach. Let the pot soak for about 1 hour before washing it with water.

Drainage

Next, you want to make sure that your pot has adequate drainage. If you bought your pots from your local gardening center, it likely already has holes. But if you’re using a decorative container or recycled pot, you may want to drill some extra holes.

Make sure that there’s at least one hole to let water through. To be on the safe side, you can drill a few extra holes around the perimeter of the pot.

Soil Preparation

Zinnia plants are quick to adapt to most soils. That said, it still pays to do a little amending beforehand.

Choose a standard potting mix. Then, add some organic compost. The compost will infuse some much-needed nutrients into the mix to make it more fertile.

Compost is excellent for growing zinnias in pots and I’ve written a post that will help you know what kind of compost to use and how to use it.

The mixing process will also loosen the dirt to ensure that it has adequate drainage.

You can take things a step further and test the pH level. Zinnias prefer soil with a pH between 5.5 and 7.5. Some slight acidity is always welcome. Incorporating a bit of peat moss into the mix should do the trick.

5. Plant zinnias in the pot

Planting zinnias is not difficult at all. Unlike other ornamental flower plants, zinnias grow very well from seed. These plants will produce seeds after blooming, so you can repeat the process next year.

Plant zinnia seeds in the pot

Start by preparing your pots and soil. It’s also a good idea to create a warm spot for the seeds to germinate indoors. Temperatures should be around 80 to 85 degrees Fahrenheit during the germination phase. This is a bit higher than the standard growing preferences of the plant, so use a grow light or heat pad to keep the soil warm.

Plant your seeds right in the pots you intend to use. Place several seeds on the top of the soil. Then, cover them with about a quarter of an inch of soil. Spritz them with water, place them in a warm spot, and wait.

How many zinnia seeds per pot?

You can plant two seeds in an 8 to 10 inch pot. You can plant four to six seeds in a 12 to 14 inch pot. And you can plant 12 to 15 seeds in a 14 to 16 inch pot. Keep a distance of 1 inch between the seeds. Later, you will thin the seedlings and only keep those that are healthy to continue growing in the pot.

You’ll grow one seedling in the 8 to 10 inch pot, two to three seedlings in a 12 to 14 inch pot, and three to four seedlings in a 14 to 16 inch pot.

In about a week, you’ll see the seedlings emerge from the soil. Continue to keep the soil moist as the seedlings get bigger.

Once they are about three inches tall, thin them. Choose a single seedling to cultivate. It should be the strongest and healthiest-looking seedling of the bunch. Remove the rest of the seedlings so that you have the appropriate amount of plants for your container.

Continue to grow the zinnia plant indoors for about 5 weeks. At that point, temperatures should be warm enough for outdoor growing. Harden the plants off over the course of the week before moving them to their new permanent home.

Plant zinnia seedlings in the pot

If you want to use seedlings instead of seeds, you’ll want to plant outside directly when the weather is right. Gently transplant the young zinnia from its nursery pot into your pot.

You’ll grow one seedling in the 8 to 10 inch pot, two to three seedlings in a 12 to 14 inch pot, and three to four seedlings in a 14 to 16 inch pot.

Keep an eye on the plant. Zinnias are notorious for having issues after transplanting. Make sure the plant is well-watered to ensure that it’s getting the fuel it needs to overcome any transplant problems.

6. Provide required sunlight to zinnias

When choosing a spot for your zinnia plants, choose an area that gets full sun exposure.

These plants need at least 6 hours of sun every day. Without it, you will experience stunted growth, fewer blossoms, and an increased risk of diseases.

Zinnias can still grow with partial shade, but the results of that growing environment may vary based on your climate. For example, plants in a warmer region can benefit from a bit of afternoon relief from the sun. But even then, there’s still a chance that your plant won’t flourish.

Air Circulation

Another important thing to consider is air circulation. The biggest issue that many gardeners face when growing zinnia is fungus and disease. These issues start to creep up when excess water is unable to evaporate from the soil.

Sun exposure is a big part of this. But, so is air circulation. Don’t place your pots too close together. This is especially important if you’re unable to give your plants full sunlight.

Make sure there’s adequate space for the plants to breathe. Air must flow through the plant to speed up evaporation and keep the soil relatively dry.

It’s important you learn to keep the right space between plants in pots. Make sure to read the seed packets for how far to plant the seeds.

7. Water zinnias in the pots

To produce those breathtaking flowers, zinnias need plenty of water. They are thirsty plants that like to have access to moist soil at all times.

Now, that doesn’t mean you should overwater your plant. As I mentioned earlier, fungal problems are a very real threat. The same goes for issues like root rot. The last thing you want is to drown your plant or stunt its growth in any way.

The trick is to find that balance between keeping the soil moist and not overdoing it.

Generally, zinnias will need about an inch of water every five to seven days. It might be more or less depending on your weather conditions. In sweltering heat, you may have to water your plant more frequently.

Before you hydrate the plant, check the soil. Ideally, you should be keeping the soil moist to depths of at least 6 inches. This is especially important for young plants. Established zinnias are more tolerant of dry soil. But either way, it’s best to keep the soil moist for continued success.

When you water the plant, focus the stream on the soil. Don’t get any water on the leaves or flowers. Doing so will only cause fungal spores to take hold.

I’ve written an ultimate guide to water your potted plants that can help you. It will teach you when and how to water the zinnias. You will also learn what is the best water you can use for potted plants.

8. Prune the zinnia plant in the pot

As an annual plant, pruning isn’t a huge concern. Zinnias aren’t like perennials. They don’t need constant pruning to ensure success during the next growing season. They die out after a year.

That said, you can do a bit of light pruning here and there to control how the plant uses its energy.

The most effective form of pruning for zinnias is deadheading. This is when you trim spent flowers once they die off. After the flower blooms, wait until it wilts and looks like it’s about to fall off. When this happens, trim the bud.

Deadheading is a great way to stave off seed formation. It tricks the plant into producing more blooms, which could extend the flowering cycle. Plus, it makes the plant look a bit tidier.

If you have a taller variety, you can also use pruning to change the way the plant grows. Pinching the tip of the plant when it’s still young will stop it from getting too tall. Instead, the plant will focus its energy on growing laterally.

It’ll produce more side branches. This results in a fuller-looking plant.

Use this technique cautiously. Pinching tall plants can also have negative effects. It may delay blooming in areas that experience cooler summers.

9. Add fertilizer to the zinnia plant

Adding fertilizer for zinnias can be beneficial to grow a lush plant that constantly produces vibrant flowers.

But, you should go overboard. These plants only need light fertilizer. They’re already prolific producers and grow pretty fast compared to other flowers. Excess fertilizer could cause some unwanted results.

If you want to apply fertilizer, use a 5-10-5 formula. Those numbers represent the amount of nitrogen, phosphorus, and potassium in the product. A 5-10-5 formula is low on nitrogen and potassium, which is a good thing for zinnias.

Your plant still needs nitrogen and potassium, but it will benefit more from the phosphorus. Phosphorus helps to convert nutrients into usable energy.

Stick to a water-soluble fertilizer for convenience. You can use the solution when watering your plant to keep things simple.

You can read my post on how and when to use a liquid fertilizer and how fast it will act on your zinnias.

When you prepare the fertilizer, you must dilute it to a quarter strength. Cut back on the recommended dosage or add four times as much water. Full-strength fertilizer will only cause overgrowth.

Apply the diluted fertilizer when the plant is still young. Plan to feed your zinnia when the seedling is still 4 inches tall. At this stage, the plant can benefit greatly from a boost of nutrients.

You can give the zinnia a second helping of fertilizer sometime in the middle of the summer. This will reinvigorate the plant and make sure that it continues to produce.

Do zinnias do better in pots or in the ground?

Zinnias do better in the ground because the root system can spread deep into the soil. This helps the plant get required moisture and nutrients. The zinnia plant can grow bigger and spread wider due to the available space for the roots and the plant.

It makes the plant hardy because it can go several days without watering. There will be plenty of moisture deep into the soil for the roots.

When planting zinnias in pots, there is a limited amount of soil available. So you need to monitor that the zinnia plant can get the required moisture and nutrients. You need to water the plant at regular schedule. You need to add the required fertilizer as well when needed.

Do zinnias spread in pots?

Zinnias don’t spread in pots because they have limited growing space. The benefit of growing in pots is you can limit how many plants grow in them. This is useful for invasive plants such as mint that can overrun the garden and prevent other plants from growing.

How tall do zinnias grow in pots?

You should choose dwarf to medium sized varieties when growing in containers. These can grow 6 to 24 inches tall. Some short zinnia cultivars are Zahara, Solcito, and Raspberry Lemonade Mix. Some dwarf varieties are Small World, Dasher, and Thumbelina.