Will Petunias Reseed In the Garden?
Petunias, with their easy color and care, are annual favorites. Depending on the variety and climate, they even reseed for a show in the following seasons. With reseeding petunias, the display is a surprise. Gardening expert Katherine Rowe explores petunias’ capacity to reseed in their optimal growing environments.
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Petunias are among the most popular summertime annuals for their waves of easy color that run until frost. With showy trumpet blooms in almost every color under the sun, they attract pollinators and energize the display. Let them quickly fill a pot, hanging basket, or border edge with their cascading stems as quintessential “spiller” and “filler” plants.
These flowers are also low-maintenance, flower reliably, and even grow from seed. In optimal conditions, and especially in climates without frigid winters, petunias may even reseed readily to expand the colony.
Shock Wave Purple Tie Dye Petunia
Shock Wave Purple Tie Dye Petunia Seeds
About Petunias and Reseeding
The popular petunias (Petunia x hybrida) we grow today are hybrids of South American native species. They made their way as a wild species to European gardens in the 1700s with the exploration of Argentina and beyond. Then, they made their way to the United States, where hybridizing resulted in most of the modern cultivars we recognize.
In their optimal growing conditions, you’ll have petunias pop up in successional seasons as seeds drift and disperse. Reseeding is most likely in areas with mild winters, and climate plays a role. Self-seeded petunias can be scrappy and durable, growing across conditions without many requirements. During the growing season, though, they rely on warm temperatures and do best with regular moisture. The best blooms come from boosting nutrients with fertilizers, and pruning helps revitalize growth mid-season.
Unless coming from a straight species, petunias often aren’t true to type from seed, meaning they won’t look like the parent hybrid. Petunias often revert to white, pale lavender, and rose-pink blooms.
Petunias sold as seeds are stable F1 Hybrids, where hand work crosses two parent species. One parent is for overall vigor and structure, while the other is for color. The “vigor” parent more closely relates to a wild strain and is the dominant species. When allowed to reseed, this one, with lavender blooms, persists over the weaker, color-selected parent.
Depends on the Selection
In addition to climate factors, whether or not petunias reseed depends on breeding. Petunia integrifolia is a wild species (not a hybrid) that naturalizes in parts of the U.S. The wildflower reseeds with magenta blooms that beckon hummingbirds and butterflies. Hearty and adaptable, it sprouts out of various soils, including poor ones, and withstands dry conditions.
Hybrids also self-sow (reverting to species characteristics). The popular Supertunia® is an exception, as the series is mostly sterile. Because it doesn’t expend energy in reproducing (seeding), it continually produces lavish blooms. It’s propagated through vegetative cuttings and is under a plant patent. Wave varieties, a more sprawling predecessor to Supertunia®, are available through seed and have the capacity to reseed, albeit in an unstable, open-pollinated form.
Types of Petunias
Petunias fall into four main groups depending on their bloom and growth characteristics.
Grandiflora
Large single or double flowers, sometimes several inches across and with ruffled or fringed edges. Long stems sprawl as summer progresses and benefit from pruning for a flush of new growth. Deadhead to promote continual flowering.
Multiflora
Yields a profusion of blooms from summer through frost, smaller than grandiflora but more prolific. Single and double-flowered cultivars are available. These hold up better under wet weather than grandiflora and with a more compact habit. Good for containers, mulitflora often benefits from deadheading.
Floribunda
Falls between grandiflora and multiflora with intermediate-sized flowers. Floribunda free-flowers until frost. Remove spent flowers for health and blooming.
Milliflora
These miniatures produce loads of one to one and a half-inch flowers. They’re very compact for the front of the border or container accents. The spent flowers are self-cleaning and don’t require deadheading.
Spreading/Trailing
Vigorous and low-growing, groundcover types boast good heat and drought resistance. Low maintenance, they’re exceptional in hanging baskets and fill up a pot. The trumpet flowers cover the length of the stem; Let them spill in the border front or over a low wall with cascading stems. These are also self-cleaning with no need to remove faded blooms.
In warm climates, try an improved variety that tolerates heat and humidity, like those in the Supertunia® series. Wave varieties in the spreading group bring a cascading form with good performance in a range of climates.
Larger and double-flowered varieties usually benefit from deadheading to maintain vigor and promote more blooms. Smaller-blooming selections usually drop naturally and don’t need it for continuous production.
Managing Reseeding
As bees, hummingbirds, and other insects pollinate each bloom, a small fruit capsule develops after flowering. The fruits develop over the season and split open at maturity to release a plethora of tiny seeds.
To foster reseeding, let petunias in a bed or pot go to seed in late summer. Stop deadheading and trimming to let them reproduce and fade. Petunia seeds are tiny; let the capsule pop open to naturally drop the fruits. In spring, look for the sprouts to appear as the weather warms. Take care not to weed them as they pop up – it takes time for them to outcompete weed competition.
To collect seeds from wild species like P. integrifolia and hybrids, too, gather the little capsules as they dry and brown. Look for the brown seed pods that form after a bloom drops. Pinch off the pods and let them dry out completely for a week or two. The pods will crack or crush easily when completely dry, revealing the minute seeds. Sift the seeds from the chaff for storing over the winter in a cool, dry place. Winter sow them in February, or direct sow them after the final frost.
If you live in a mild winter climate and don’t want your reseeding petunias to crop up with abandon, deadhead spent blooms or pluck off seed pods as they form. Stick with a Supertunia® that doesn’t naturally reseed.
Sowing Seeds
When it comes to sowing purchased or collected seeds, start petunias indoors for a head start on growth to maximize the flowering season. Or, consider winter sowing them outdoors in protective containers. Lastly, direct sow them after the final frost if you have a long growing season. Ideal soil temperatures for germination are between 68-85°F (18-29°C).
Petunia seeds need light exposure to germinate, so there’s no need to cover them with soil. Lightly press them onto the soil surface of the potting mix in a tray, and moisten thoroughly. Keep the media moist and place the tray in a warm, bright spot out of direct sunlight. Expect to see sprouts in a week to ten days, or as many as 30 days, depending on the setting and variety.
Favorite Varieties From Seed
Growing petunias from seed offers an economical way to grow the annuals in large numbers. It also lets us get creative and selective, from old-fashioned varieties to swirling colors. Here are a few highlights that may self-sow for future color:
‘Shock Wave® Purple Tie Dye’
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botanical name Petunia x atkinsiana ‘Shock Wave® Purple Tie Dye’ |
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sun requirements Full sun to partial shade |
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height 7-10” |
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hardiness zones 10-11 |
‘Shock Wave® Purple Tie Dye’ brings striking variations in deep violet and white blooms. No two are alike in this bold contrast. The petite plants stay under one foot tall but spread up to 30 inches. The tidy, compact ‘Shock Wave®’ has a mounding, spreading habit.
‘Shock Wave® Purple Tie Dye’ is a color-shifting tapestry, as its purples change with growing conditions like light and temperature. The flowers on the floriferous low-growers are one and a half to two inches wide. They’re a kaleidoscope of purple in containers, hanging baskets, window boxes, and small spaces.
‘Petite Charmer Blend’
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botanical name Petunia x atkinsiana ‘Petite Charmer Blend’ |
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sun requirements Full sun to partial shade |
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height 8-14” |
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hardiness zones 10-11 |
An old favorite, ‘Petite Charmer Blend’ is compact and neat with an array of colorful one-and-a-half-inch blooms all season. The singular bell blooms in different colors and shines against lush, leafy stems.
‘Petite Charmer Blend’ offers a mix of shades in red, pink, white, salmon, and purple. There’s also something dynamic to show with this composition, small in stature but big on color.
‘Garden Party’
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botanical name Petunia x atkinsiana ‘Garden Party’ |
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sun requirements Full sun to partial shade |
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height 10-15” |
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hardiness zones 10-11 |
‘Garden Party’ is a sweet watercolor blend of pinks, purples, and reds. In varying shades and with delicately contrasting veins, the large blooms usher in the cheer of a vibrant summer garden.
‘Garden Party’ has large, tissuey flowers that are three inches wide. Spreading only one foot, they grow upright and mound as full container specimens that won’t sprawl or run.
