Petunias are a beloved fixture in gardens, admired for their vibrant colors and prolific blooms from spring until the first frost. Beyond their visual beauty, many gardeners discover their delightful fragrance, which transforms displays into a sensory experience, especially as evening approaches. This pleasing scent adds depth to containers, hanging baskets, and garden beds, enhancing outdoor spaces.
Describing Petunia Fragrance
Petunia flowers offer a diverse palette of scents, varying significantly by type. Older, “heirloom” varieties, especially those from Petunia axillaris, are known for their strong, often musky or sweet fragrance. This wild species, native to South America, features large, white, night-blooming flowers with a pronounced aroma. In contrast, Petunia integrifolia, with smaller violet blooms, is generally less scented.
Modern hybrid petunias often prioritize bloom size, count, or color over fragrance. However, many contemporary cultivars still retain or have been bred for appealing aromas. Scents can range from classic sweet floral to spicy, citrusy, or clove-like, with hints of honey, vanilla, or rose.
Specific fragrant varieties offer distinct aromatic experiences. ‘Evening Scentsation’ has indigo-blue to soft purple flowers with a sweet perfume, notes of hyacinth, honey, and rose, intensifying in the evening. ‘Blue Storm’ provides vibrant blue-purple blooms with a sweet, jasmine-like scent. ‘Tumbelina Candyfloss’ produces double pink flowers with a sweet, sugary fragrance.
Other notable fragrant types include:
‘Daddy® Blue’ offers an old-fashioned sweet scent from its pale-blue flowers with dark purple veins.
The ‘Prism Sunshine’ grandiflora variety, with yellow and white blooms, is scented, particularly at night.
‘Carpet Pink’ provides a sweet, classic petunia scent with light notes of honey and vanilla, most pronounced in the evening.
‘Night Sky’ petunias, known for their speckled appearance, can also possess a sweet fragrance.
Factors Affecting Petunia Scent
A petunia’s fragrance intensity is rooted in its genetic makeup. Plant genes dictate the production of volatile organic compounds (VOCs) that create its aroma. These VOCs are actively synthesized and released by the plant. Common types responsible for petunia scents include benzenoids and phenylpropanoids.
Scientific understanding indicates that VOCs are actively transported from plant cells, not simply diffused. This mechanism allows the plant to control the timing and rate of scent emission, which is precise for attracting pollinators. The gene ODORANT 1 (ODO1) also promotes the production and release of these floral scents.
Many petunia varieties, especially those from Petunia axillaris, exhibit nocturnal fragrance, becoming stronger after dusk. This timing is a biological adaptation to attract nighttime pollinators, primarily hawk moths. The plant’s internal circadian clock governs this daily rhythm of scent release, with the LHY gene playing a role.
The morning activity of the LHY gene represses scented chemical production by interfering with the ODO1 gene. As the day progresses and LHY activity decreases, ODO1 increases the synthesis of fragrant compounds, leading to peak scent emission in the evening.
Environmental conditions also influence petunia fragrance. Temperature has a complex effect; while increasing temperatures can decrease scent production in some hybrids, Petunia axillaris scent emission has been observed to peak at certain temperatures. Optimal temperature ranges for scent production can vary by species or hybrid. Humidity and light intensity also impact volatile emission rates. Healthy plants with adequate nutrients and hydration generally produce a more robust fragrance.
Maximizing Petunia Aroma
To fully experience petunia aroma, select the right varieties. Prioritize older, “old-fashioned” white petunias or modern cultivars bred for strong fragrance, such as ‘Evening Scentsation’, ‘Rainmaster’, ‘Blue Storm’, ‘Tumbelina Candyfloss’, ‘Daddy® Blue’, or ‘Prism Sunshine’. These varieties offer pronounced scents, from sweet to spicy or clove-like.
Strategic placement enhances the aromatic experience. Plant fragrant petunias near outdoor seating, along walkways, or beneath windows where their scent can drift indoors, especially in the evening. Containers and hanging baskets are excellent for placing these scented beauties close to living spaces.
Optimal growing conditions support vigorous growth and robust scent production. Petunias thrive in full sun, needing at least six hours of direct sunlight daily for abundant blooms and fragrance. Plant them in rich, well-drained soil amended with organic matter for steady nutrient supply.
Consistent watering is important for plant health and scent quality. While petunias tolerate some drought once established, regular watering, typically once a week for in-ground plants, promotes continuous blooming and fragrance. Container-grown petunias may require more frequent watering, sometimes daily during hot weather.
Petunias are heavy feeders, so consistent fertilization is beneficial. Apply a balanced, water-soluble fertilizer weekly or a slow-release granular fertilizer monthly to support healthy growth and encourage more flowers, which means more scent. Regularly removing spent blooms (deadheading) redirects the plant’s energy from seed production to new flowers, extending the fragrant display.