The taller varieties of balloon flowers can become a bit floppy. You can stake them or plant them in clumps to let them support one another. Start with nursery plants or grow your balloon flowers from seed.
Light
You will get the most flowers if you plant balloon flowers in full sun (at least six hours of sunlight on most days). However, they will be fine in part shade and might actually prefer some shade from where the afternoon sun is especially hot.
Soil
Balloon flowers prefer organically rich, loamy soil that has good drainage. They don’t grow well in dense soil, such as clay. They like a soil pH in the 5.5 to 7.5 range.
Water
Keep the soil of young plants consistently moist but not soggy. Once established, balloon flowers like a moderate amount of moisture in the soil, but they can tolerate short periods of drought. They won’t need a lot of supplemental watering unless you have a long period without rainfall that causes the soil to dry out.
Temperature and Humidity
Balloon flowers are hardy and do well in USDA growing zones 3 to 8. Their ideal temperature range is between 60 and 80 degrees Fahrenheit, but they can withstand higher temperatures if they have some shade in the afternoon. Frost can kill young plants and will cause established plants to die back into the ground in the fall. Balloon flowers tolerate both humid and dry air conditions, provided they have the right amount of soil moisture.
Fertilizer
Balloon flowers typically don’t need supplemental feeding if you have rich soil. But a layer of compost in the fall can help them replenish the energy they expend blooming during the growing season. If you have poor soil, use an all-purpose, slow-release fertilizer in early spring.
Types of Balloon Flowers
There are several popular varieties of balloon flowers, including:
Platycodon grandiflorus Astra series: This type grows double flowers with 10 petals in blue, pink, or white. They’re an ideal choice to start from seeds.P. grandiflorus Fuji series: This is the most commonly sold variety, as well as the tallest, with 30-inch stems and flowers in blue, pink, or white.P. grandiflorus ‘Komachi’: The purple-blue flowers in this variety stay in their puffy pillow stage even after blooming.P. ‘Sentimental Blue’: This dwarf variety grows about 6 inches tall with lots of 1- to 2-inch purple flowers.
Pruning
Pruning generally isn’t necessary with balloon flowers, though you can do so for appearance. To achieve stockier plants, you can cut back tall stems by about half in the late spring. This can help to prevent the plants from flopping over. Also, deadheading your plants (removing spent blooms) will keep them looking good and repeatedly blooming. Don’t remove the whole stem, just the faded flowers. The remaining buds on the stem will continue to open.
Propagating Balloon Flowers
Balloon flowers are favorites of gardeners because they are solid and fast performers so the more the merrier, but you have to be careful how you propagate the plant. Propagating by division is generally not recommended for balloon flowers because the deep taproots do not like being disturbed. Instead, you can propagate by taking stem cuttings.
How to Grow Balloon Flowers From Seed
Start seeds indoors in the early spring about six to eight weeks before your area’s projected last frost date, using seed starter mix or ordinary potting soil. Barely cover the seeds with 1/16 inch of soil. Place the container in a warm location until the seeds germinate. After the weather has warmed, you can transplant the seedlings outdoors. If you plant seeds directly in your garden, do so after your last frost date, but know they likely won’t flower in their first year.
Common Pests and Plant Diseases
Balloon flowers generally attract slugs and snails, as do many other outdoor bloomers, which can be coaxed off the plants with bait. However, the plant may become afflicted with crown rot, root rot, botrytis gray mold, powdery mildew, or fungal leaf spot. Crown and root rot may cause plants to die over the winter. Leaves presenting powdery spots, mottling, or blotching can usually be treated with a fungicide. Quickly discard plants with gray mold so it doesn’t spread, then use a preventative fungicide on remaining plants.
