11 Tips for Growing Beautiful Zinnias in Pots

Zinnias are widely revered as a bright and cheery annual flower option, easy to grow in many different soil types. They work well as border flowers, and their height makes them perfect for the backdrop to landscaped plants. However, they look cute as can be in patio containers that you can move around to follow the sun or accent seating areas. If you want to grow zinnias in pots, we’re here to help with some easy tips!  

Here are 11 simple things you can do to grow beautiful zinnias in containers. 

Start From Seed

Zinnia seeds are pretty large, and most varieties offer a high germination rate, so starting them from seed is an easy choice. You can either start them indoors in cells and then transplant them into a pot a few weeks later or sow them directly into the container of your choice. You choose!

If you direct-sow them in a pot, space them according to your pot size. Since they are a bit larger, bury them about a ½ inch down. Do not start any sooner than six weeks before your last possible spring frost. This will allow them to mature enough before planting outside but not long enough to become rootbound or stressed. 

Seeds will germinate within 5-7 days when the soil temperature is between 74-80°, and even quicker when heat mats are used. Water the seeds in well, but do not fully saturate the soil. 

Do not transplant zinnias into outside soil until temperatures are consistently over 60° to reduce the risk of transplant shock. 

Select Appropriate Varieties 

If you are new to zinnias and want to grow them in pots, one of my no-fail favorites is ‘Benary’s Giant Blend.’ This will allow you to see all the colors Benary’s provides and pick your favorites for next season. These stems can get quite tall, so be prepared with a properly sized container offering some support with enough room to space them properly.   

If you’d prefer a more compact zinnia to grow in pots, the award-winning ‘Profusion’ series is a bushier, colorful option that will turn heads. 

The ‘Cactus Zinnia Flower’ offers a funky look and adds visual interest to your front stoop or back patio. Furthermore, ‘Double Zahara™ Brilliant Mix’ is a new, mum-like zinnia perfect for bred for powdery mildew resistance. 

Whatever variety you select, only purchase seeds from a reputable source. 

Use Proper Potting Soil

Use something with well-balanced nutrients that can drain well. Feel free to add something absorbent, such as vermiculite or peat moss, to help store moisture.

Mixing in well-aged manure or compost is helpful when growing zinnias in pots, as they are moderate feeders and are in the ground for quite a while. 

Choose An Appropriate Container

Today’s gardeners have so many more options than just window boxes or ceramic pots. To grow zinnias in pots, you need the right vessel. Here are some of my favorites:

• Grow bags have become very popular over the past few years due to their built-in drainage material, ease of moving, and durability. The water drains right out, so it’s nearly impossible to overwater. Most bags on the market offer handles that make it easy to move around your potted plants or move them inside during inclement weather. 
• Permanent raised beds are a gardener’s new best friend. I use them at our farm to keep herbs like mint and oregano from spreading, but they’re also perfect for annual flowers. Growing in raised beds provides increased soil health, improved drainage, a clean look, and less bending over to harvest.
• Hanging baskets add dimension and height to any garden display. Try growing a shorter cultivar and something that will hang over the sides to add a little drama. 
• Classic ceramic pots are still great to grow in! These add a little class to a patio or outdoor landscape. There are also BPA-free plastic pots with a bottom-watering tray that’s perfect if you have to leave your plants to fend for themselves for a few days. 

Choose A Good Location 

Zinnias will thrive in full sun out of harm’s way from strong winds. However, partial shade will be just fine as well.

As previously mentioned, zinnias make a great border wall planting and look lovely along the outer edge of a small flower plot. If you grow zinnias in pots, you can show them off on the front porch, back patio, or even in garden beds. Move them around occasionally for fun! 

Pinch Back When Plants Are Young And Deadhead Often

It may seem counterintuitive to pinch back young plants waiting to be transplanted. However, think of pinching back your zinnias to encourage them to get established, send out side shoots, and prepare them for a long season of abundant, continuous blooms.

Studies have shown that pinching back in certain cultivars also creates a bushy, shorter plant with thicker stems, which is ideal when growing in containers. Sometimes, cutting down what seems like a perfectly good flower seems sacrilegious, but you’re paying it forward to your future garden.

Deadheading refers to cutting back unwanted, misshapen, or passed-by flowers. If too many days have passed or lots of rain browns your flowers, go through with a pair of sharp snips and cut them down to above a node near the base. Keep at least two sets of leaves intact to ensure future growth.

Cutting back in this way will not only clean up your flower patch but also creates more airflow and provides a space for new blooms. In about a week or so, you should start to see new blooms appearing. And just like that, your zinnias are freshened up!  

Water Regularly 

Zinnias are pretty low-maintenance regarding water since they do not require much, about an inch per week. But, since zinnias love to be in full sun and love the heat, pay close attention to their water levels and don’t let them dry, especially if you grow in a hot and sunny climate.

The thing to remember when growing zinnias in pots is that the roots have no place to reach down in search of water. They are solely relying on you for care. 

Water at the base of plants, preferably in the early morning versus at night. This will allow plants time to soak in the water and dry out during the day since fungal disease can spread in wet conditions.

During hot spells, water twice daily. Do the finger test if you’re unsure if your zinnias need to be watered. If the soil feels dry about two inches down, they need water.

Pest Control 

Zinnias may be one of the easier annual flowers to grow, but they certainly come with their pests. Japanese beetles LOVE to munch on zinnia leaves and flowers. In fact, it’s one of their favorite things to do.

If you have used Japanese beetle traps before, try hanging one near your zinnias, but not directly next to them. This way, as they head toward their snack, the lure of the trap will be stronger, hopefully diverting them. 

Alternatively, keep a jar full of soap water nearby and hand-pick the beetles each morning, dropping the beetles into the jar. Then, dust the plants lightly with diatomaceous earth. This should deter them from landing on your plants or luring other beetles to your zinnias for mating. 

You may also encounter spider mites and aphids, which can usually be controlled by spraying your plants with insecticidal soap.  

Fertilize 

When transplanting zinnias, mix a tablespoon of bone meal into the top few inches of soil. This will direct the focus beneath the soil and encourage a strong root system. 

Zinnias will benefit from a monthly feed of fertilizer that’s higher in phosphorus than nitrogen to help promote continuous blooming and overall health. Healthy plants are better at fending off disease and warding off pests. However, soil testing should be done pre-season to determine the exact amount needed in your garden. 

Be On Alert For Diseases

It’s important to know when conditions are right for disease formation and what to watch for so you can act accordingly. A few heavy hitters to be on the lookout for are: 

• Powdery mildew will thrive in warm, dry conditions and can be identified by grayish-white spots on buds and leaves. Preventatively, space your zinnias at least a foot away from one another so there is ample airflow. If you spot powdery mildew, spray thoroughly with a copper fungicide that prevents future spread. Clear out any diseased debris, including lower leaves and flower heads, and take them to a burn pile.
• Southern blight occurs during extended periods of wet weather and when leaves remain wet. The fungus causing Alternaria zinniae overwinters in debris or can come from contaminated seeds. Symptoms include small, reddish circles with light centers. Leaves may become brown and dry. Prevention includes good airflow, spacing out plants properly, avoiding extended wet periods, debris and weed-free gardens, and cleaning all seed-starting supplies and tools.
• Bacterial leaf spot symptoms include small, circular purple spots on leaves which show up after extended rainfall. If spots mesh together, they may look more angular, and a yellow halo may occur. Growers can spray copper fungicide on zinnias after rainy periods to prevent the fungus from spreading and causing damage. Always spray copper in the evening. 

Keep Stress At A Minimum 

Zinnias are very sensitive to cold and other environmental stressors like drought and flooding. If you start them in cell trays, do not allow them to become root-bound before transplanting them into their containers.

This could cause transplant shock, and if you have selected a double-bloom variety, they could revert back to single-blooms due to the stress, which is disappointing, to say the least. Take it from me. I have learned this first-hand! 

Zinnias will perish even after a light frost, as they have zero tolerance. As temperatures cool off in the fall months, growth and blooms will begin to slow. It’s always sad to see them go away for the season, but if you treat them well from the beginning, they will provide an abundance of brilliance all summer long.