Are you interested in growing zinnias in pots but unsure where to start? Whether you're a seasoned gardener or a novice enthusiast, cultivating these vibrant blooms in pots is easy to do and provides a wealth of color cut flowers all season long. From growing zinnia seeds indoors to understanding their care and sunlight requirements, this guide covers everything you need to know to grow an abundance of zinnia blooms in a container garden.
Skip Ahead: Soil and pots • Starting seeds • Transplanting zinnias • Spacing • General care • Fertilizing • Zinnia varieties for containers • FAQ
Selecting soil and pots for zinnias
Selecting the right soil and pot for zinnias is the first step to helping them thrive. Zinnias like well-drained soil rich in organic matter. A standard potting mix is ideal and should offer plenty of drainage.
When it comes to pots, choose containers that are at least 18 inches deep to accommodate zinnia roots. Zinnias grow roots that are one or two feet deep, so they'll do well in pots up to about 24 inches deep. Terra cotta or clay pots are excellent choices in very wet areas, while plastic or glazed pots can help to conserve water use in dry or very hot areas.
Regardless of which type of pot you choose, make sure it has drainage holes and prop it up on feet to avoid the pot sitting in a pool of water.
Starting zinnia seeds indoors
Starting zinnia seeds indoors helps ensure that you'll get blooms all summer. To start, you'll need seedling trays, a seed starting mix, and a packet of zinnia seeds. Planting zinnia seeds directly into their final pots is possible in warm zones, but sowing them into cell plugs or a seedling tray is the most space-efficient way to start indoors.
Here's how to start your seeds:
- Fill the trays or pots with a well-draining seed starting mix. Water the mix thoroughly before adding the seeds. Sow the zinnia seeds thinly on the surface of the soil, gently pressing them down without covering them. Zinnia seeds require light for germination, so avoid covering them with too much soil. A light covering of soil or vermiculite will help keep the seeds in place when you water them.
- Water in the seeds generously. This will ensure they get good contact with the soil.
- Place the trays or pots in a warm, sunny place or give them artificial light.
- Water the seeds lightly when the soil dries out. This ensures that when seeds do start to sprout, they'll have access to water.
- Zinnia seedlings should emerge within 7 to 10 days as long as they're kept somewhere with daytime temperatures around 70-75°F.
- Transplant the seedlings into larger pots or cells once they have developed their cotyledons (first sets of leaves). At this point, give them a potting mix that will provide nutrients to help the plants grow further.
- Harden off the seedlings gradually once the first sets of true leaves emerge and the seedlings are a few inches tall. You can start hardening off your zinnias by putting them in a shady spot outside for a couple of hours daily and gradually increasing their time outdoors until they can stay outside overnight. This should take at least a week and can take two or three.
Transplanting zinnias into pots
Once your zinnias are acclimated to being outside, and have developed a sturdy stem with multiple sets of true leaves, they're likely ready to plant out. Here's how to transplant them into containers:
- Turn the start pot upside-down to pop out the zinnia. If the plant's roots hold the soil in place, it's ready for transplanting.
- Fill your pots with a standard potting soil.
- Dig a hole slightly larger than the root ball of the zinnia seedling and carefully place it in the center. Gently pat the soil around the base to secure the plant.
- Water thoroughly and place the pots in a location that gets at least six hours of sun daily.
Read More: The 9 Best Zinnia Companion Plants
Zinnia spacing in containers
Zinnias don't like to be crowded, and planting zinnias too closely together encourages powdery mildew. To avoid this, create room for air circulating by spacing zinnia plants at least 12 inches apart if you're growing a container-friendly variety. For larger varieties, give each plant its own pot, or at least 18 inches of space.
General care for zinnias
Zinnias are low-maintenance flowers, but some attention will help them to produce an abundance of flowers all summer and into the fall. Here's how to care for zinnias in pots:
- Watering: Keep soil consistently moist, but avoid waterlogging it. In pots, this will take more regular watering than the plants would need in the ground. Watering the soil directly will help to prevent the leaves from developing mildew and other fungal diseases. The best time to water zinnias is in the morning, so that the plants have cool, moist soil throughout the day instead of overnight.
- Pruning : Zinnias don't require pruning, but cutting back spent flowers to the next leaf node promotes bushier growth and more blooms.
- Deadheading: To deadhead zinnias, use pruners, a knife, or sharp scissors to remove spent flowers down to the next leaf node. Regularly cutting flowers to take inside also helps stimulate continuous blooming throughout the season.
- Fertilization: Zinnias like rich soil but typically don't require fertilization. If you notice signs of nutrient deficiency, top dress the container with compost.
- Mulching: When potting, mulch around zinnias to help the soil retain moisture and to regulate soil temperature.
Fertilizing zinnias
Zinnias like fertile soil, and zinnias planted into containers can suffer from nutrient run-off after a few months of watering. To fertilize zinnias, you can simply top dress them with a gentle organic fertilizer, comfrey leaves, homemade compost, or comfrey tea.
What are the best zinnias for containers?
Most varieties of Zinnia elegans grow two to three feet tall, but some have been bred to grow well in pots. These zinnias typically grow smaller blooms on shorter stems. Here are some of the best zinnias for container gardens:
- Zahara: Produces small, 2 1/12 inch double blooms in a variety of colors. Double Zahara Salmon grows consistently pink blooms, while Double Zahara Yellow produces lemon yellow blooms. Both grow 16-20 inches tall and wide.
- Pinwheel mix: Small, single bloom flowers that look almost like brightly colored daisies. Grows 3 ½ inch flowers on 12 inch stems.
- Northern Lights blend: Single bloom purple, pink, and red zinnias with 4-5 inch flowers that grow 24-36 inches tall.
- Thumbelina: One of the smallest zinnia varieties, Thumbelina zinnias grow just 10-16 inches tall. Produces white, yellow, red, and pink flowers that are just 1-1/12 inches. Ideal for smaller pots, with each plant needing only 8-10 inches of space.
- Persian Carpet: A different species of zinnia (Zinnia haageana). Has narrower leaves and a more compact, bushy growing habit than the standard, tall Zinnia elegans. Grows orange, red, and god variegated flowers on 12-16 inch tall stems.
Will zinnias grow in shade?
While zinnias can grow in part shade, they'll be more susceptible to downy mildew and won't produce as many flowers.
Zinnias prefer full sun. They're originally native to the southwestern US, Mexico, and Central America, so they're adapted to wide open spaces in very sunny, intensely hot environments. With containers, it's easy to replicate that environment as long as you have full sun-- that's 6-8 hours of sun each day.
Do zinnia do well in pots?
Zinnias can grow very well in pots as long as they're given full sun, good drainage, and airflow. They're some of the easiest flowers to grow from seed, and they're incredibly low maintenance to grow in containers. You can even grow dwarf zinnia varieties that are suited to growing in smaller pots.
How do you keep zinnias blooming?
You can keep zinnias blooming right up until your first frost by deadheading them. Deadheading refers to the practice of cutting or pinching off the flowers so that the plant keeps producing new blooms. Put simply, as long as you keep cutting flowers, your zinnias will keep producing them.
Will potted zinnias come back?
Potted zinnias are annuals, so they won't come back after the growing season ends. They might reseed in their pots, but you can also easily collect zinnia seeds so that you can resow them next year.