Zinnias are one of the most underappreciated garden staples out there. Depending on the species, you can grow these beautiful annuals from the inhospitable USDA hardiness zone 2 to the southern zone 11.
They’re also excellent self-seeders, meaning you can have them come back year after year by letting the bloom fade. But zinnias have another side to them that few people know about – they can be grown in containers!
So here’s everything you need to learn about caring for potted zinnias.
How To Care For Zinnias In Pots
Growing zinnias in pots aren’t difficult, but there are a few things to remember.
These mainly revolve around the fact that the soil is more constrained in a container than in a garden.
Size Matters
Size isn’t always essential, but many plants in the sunflower family are notorious for becoming top-heavy when in full bloom.
Picking the wrong size zinnia could result in the plant toppling over or growing poorly due to the size of the container.
You can usually get away with a decent-sized plant for regular pots. However, the tallest varieties will need extra support.
Add dwarf varieties to window boxes and hanging baskets or pots, but avoid window boxes for larger varieties.
To choose a suitable container size, look at the spacing requirements on your package of seeds or as specified for your particular zinnia.
Use this measurement to determine the diameter of your pot. For example, a zinnia that needs 12” inch spacing will do well in a 12” inch pot.
If you go too small, your plant might become root-bound. And a too-big container could result in fungal infections or other health problems.
Soil Needs
Zinnias prefer an organically rich, well-draining potting mix.
An African violet mix with added perlite or vermiculite is a perfect example. You can also use your favorite soil-free blend to great effect.
Lighting and Temperature
Though not called sunflowers, zinnias do love the light! So whether growing your zinnia from seeds or transplanting one from your nursery into a pot, make sure it gets a nice, sunny window.
They need at least 6 hours of direct sun daily to remain strong and healthy.
In particularly harsh climates, choose a window facing east or west to catch the sun when it’s a bit more gentle and provide a little shade during midday.
Note that you can also augment natural lighting with grow lamps.
Indoor settings provide the perfect temperature range. Zinnia will generally only suffer if exposed to temperatures of 50° degrees Fahrenheit or below.
The average household humidity of 30% to 50% percent is also perfect for these plants.
Food and Water
The soak-and-dry method is perfect for zinnias and will help prevent accidental overwatering.
Stick your finger straight into the soil and water if it feels dry 1” inch down.
Use room temperature distilled water or natural rainwater, and pour slowly enough that the soil can absorb as quickly as you add. Stop when water begins to seep through the drainage holes.
As for feeding, a monthly dose of half-strength balanced liquid houseplant fertilizer during the spring and summer is all you need.
Stop feeding when fall comes, as the plant will be nearing the end of its life and won’t produce any more new growth.
Maintenance
Zinnias don’t need much maintenance if you’re watering them correctly.
The vast majority of problems potted zinnias face relate to improper watering or lack of proper lighting.
Deadheading is optional, but doing so will result in a longer bloom time and a reduced chance of getting viable seeds. But you can keep a couple of flowers for this purpose.
When your plant’s life ends, you can discard it and reuse the container next year – although you might want to use fresh soil.
Final Notes
Zinnias are a remarkable and very forgiving genus of flowers. They’re non-toxic to humans and pets, and indoor settings are perfect for their needs.
It’s not uncommon to start zinnias from seeds before transplanting them outdoors. Consider potting a couple of next spring to keep indoors or on a patio or deck.
You might find that once you’ve had a potted zinnia, you’ll want to have some every year!