Growing Zinnias In Pots: How To Care For Potted Zinnia Plants

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Zinnias in pots are sometimes overlooked for fancier plants. But these little beauties have an awful lot to offer. Zinnia flowers have a wide range of shapes. Enjoy a single petal layer to fluffy, dome-like flower heads depending on the species or cultivar.

Besides the flowers, potted zinnias are huge butterfly magnets. The smaller varieties adapt well to life in containers. Zinnias are perfect for window boxes, patio or porch pots, or brightening up the kitchen table.

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How To Care For Zinnias In Pots?

Growing zinnias in pots can be surprisingly easy. Here’s what you need to know to enjoy these wonderful plants almost everywhere.

Starting from Seeds

Chances are, you’ll be growing your first zinnias from a seed packet. You can also harvest or collect seeds from old zinnia flower heads.

You’ll want to sow the seeds approximately 5 to 7 weeks before the final frost.

Here’s what you need to do:

  • Starting them off in a peat pot or cardboard egg carton means transplanting is a snap later.
  • Fill them with a sterile starter potting mix and sit your starting containers in a shallow water tray.
  • Once the top of the soil feels damp, remove the pots and add 2 to 3 zinnia seeds in each compartment or pot.
  • Space them evenly and at a depth of ½” inch.
  • Place a clear plastic bag over the peat pots (or loosely lay some plastic wrap over the egg carton) to help keep humidity in without restricting airflow.
  • Find a spot for your plants where there’s bright, indirect light and a temperature range of 75° to 80° degrees Fahrenheit.
  • Gently lift the plastic and mist as needed to ensure the soil remains lightly moist, and you should see them beginning to sprout in about 7 to 10 days.

At this point, you can remove their cover and place them on a windowsill to encourage faster growth.

Once the seedlings have two leaves, separate them, so there’s only one per container or compartment.

You can plant the ones you think out in additional peat pots or cartons, or you can plant them directly into pots.

Meanwhile, you can separate the egg compartments and plant each section (and each peat pot) into its own pots, letting nature compost the starting containers as the plant grows.

Choosing the Right Pot and Soil

The container should be 8″ to 10” inches deep and just as wide as the rim for potting purposes.

You can use elongated containers for multiple zinnias, but keep the width in a multiple of 8″ to 10” inches to ensure each plant has adequate breathing room.

Overcrowding zinnias is a common mistake that can easily lead to disease.

Terra cotta pots work very well, and you can even grow them in plastic hanging baskets, but whatever container you use will need to have adequate drainage holes.

Zinnias love organically rich, well-draining soil but can handle most soil types.

For potting purposes, we suggest Miracle-Gro, which is cheap, has a great reputation for quality and tends to provide everything your zinnia will need – including perlite already added to the soil!

Just be sure to moisten the soil before transplanting, including when adding the seed container.

Related: What To Plant As Zinnia Companion Plants?

Environmental Needs

Zinnias absolutely love the light, so make sure you put them somewhere. They’ll get full sunlight access for at least a few hours daily.

You may need to give them a little light shade at midday if you live in a region where the sun can get pretty harsh.

Indoors, you can augment natural sunlight with grow lamps, but avoid outdoor spots that get too much shade during the day, such as north-facing porches or decks.

Regarding humidity, zinnias aren’t keen on high humidity levels and can easily fall prey to fungal infections.

A range of around 30% to 50% percent humidity should be plenty for any type of zinnia in your potted collection.

Normal household temperatures are perfect for zinnias, but anything below 50° degrees Fahrenheit can severely harm the plant.

Likewise, outdoor plants may wilt if the temperatures exceed 85° degrees Fahrenheit.

Food and Water

Potted zinnias do well with a balanced liquid houseplant fertilizer diluted to half strength.

Give this to them monthly through spring and summer, but cut back when autumn hits.

The soak and dry method is perfect for these plants, and you’ll want to water if the soil feels dry 1” inch deep.

Remember to pour slowly and evenly, working your way around the container until you see moisture seeping through the drainage holes.

You should avoid getting the foliage wet when possible, increasing the risk of fungal infections.

Should You Deadhead Zinnias?

Zinnias tend to maintain themselves, but deadheading can be a great way to keep those blooms coming for as long as possible.

The downside to deadheading a zinnia is that it interrupts the seeding process, which means you may need to purchase more seeds for next year instead of harvesting them yourself.

Risks and Concerns

Zinnias aren’t without their issues, and the risk of fungal infections due to overwatering, high humidity, or infestations can be higher than many of your other plants.

The good news is that proper care will reduce this risk to practically zero.

Aster yellows is a bacterial disease that cannot be treated or cured, and any infected zinnias will need to be destroyed and the soil discarded.

Bacterial leaf spot is another disease caused by getting the leaves wet.

Root rot is one of the scariest diseases, and both the bacterial and fungal forms are caused by overwatering.

Many pests can also attack zinnias, with aphids and spider mites being the most common indoor pests.

Outdoors, Japanese beetles, leafhoppers, and several caterpillar species are known to attack the plant.

To finish up on a positive note, zinnias in pots are completely safe and non-toxic to both humans and pets. Zinnias are a feel-good plant that adds beauty without risk to any home.

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