Petunia, pronounced [peh-TEWN-ya], is a genus of nearly 35 flowering plant species. It belongs to Solanaceae, the nightshade family, native to South America.
The common garden petunia (petunia atkinsiana) is a popular decorative plant. Its beautiful, trumpet-shaped flowers make it popular for summer window boxes and flowerbeds.
The plant’s botanical name is petunia hybrida. The majority of petunia species are annual herbs.
Although the common garden petunia is a herbaceous perennial, it’s more commonly cultivated as an annual. Its flowers bloom from early summer through frost.
Common petunia flower names:
- Night Sky
- Chocolina
- Pirouette Red
- Amore Queen of Hearts
- Mirage Red Morn
Petunia Care
Size and Growth
There are hundreds of petunia varieties, falling into different categories based on size and growth habits.
- Milliflora is miniature, with even smaller plant size and flowers
- Multiflora has a greater number of smaller flowers
- Grandiflora has the biggest flowers
- “Wave” petunias, like other “spreading” types, grow fast and can fill in vast spaces
Flowering and Fragrance
Petunia flowers bloom from spring until frost. They come in a wide spectrum of colors and patterns—smooth and ruffled petals; single and double blooms; solid single, veined, striped, or picotee-edged colors. They also have varying fragrances.
Light and Temperature
A location with lots of light is the key requirement for growing petunias well. They need at least 5 to 6 hours of direct sunlight and perform even better when directed to full sun all day.
Petunias tend to produce fewer flowers if they get too much shade. When daytime temperatures range between 70° and 85°degrees Fahrenheit, the seeds begin to develop.
According to the University of Minnesota Extension, petunias thrive in temperatures that don’t fall below 55° degrees Fahrenheit at night and 65° degrees during the day.
Watering and Feeding
- Petunias don’t demand lots of watering. While “spreading” types do require frequent watering, the rest can tolerate lots of heat
- Thorough watering once per week generally suffices, except in poor weather conditions
Soil and Transplanting
While the soil doesn’t have to be very rich to grow petunias, it must be well-drained. Also, make sure to condition your garden soil with organic matter, such as compost, peat moss, or manure.
For planting in a garden, you’ll need a balanced fertilizer, like 8-8-8, 10-10-10, or 12-12-12. You need to work it into the soil at a rate of two pounds per 100 square feet. From early to mid-July, start using a liquid fertilizer every three weeks.
For planting other containers, like window boxes, merge a controlled-release fertilizer into the soil. From early to mid-July, fertilize every two weeks with a liquid fertilizer that’s designed for flowering plants.
Weekly fertilization is required for “spreading” types, both in gardens and containers.
Grooming and Maintenance
By the middle of summer, most petunias become leggy and blossom from leafless stems. To keep your petunias flowering well, prune the shoots back to nearly one-half their length. Doing this enhances branching and flowering.
Fertilize and water the plants thoroughly after pruning to encourage new growth and blossoms. The plants might appear ragged for a while but will recuperate with more blossoms and color.
Remove dead or faded flowers (a practice called “deadheading”) to encourage blooming and keep your flowers looking fresh, especially larger-flowered petunias.
While it might not be practical with deadhead masses of petunias in your garden, deadheading is imperative for flowering annuals in pots.
How to Propagate Petunia
The ideal way to grow more petunias for next year’s garden is by rooting petunia cuttings, as there are a couple of potential problems with propagating petunias.
If you save the seeds to plant them the following year, the seeds you’ll collect simply won’t breed properly then.
Here’s how you can propagate petunias:
- Pick healthy, strong young stems that are not flowering.
- If you don’t find the right growth, cut back one to two stems from the plants to support regrowth.
- Cut just below a node or leaf joint. Take cuttings 3-4 inches long.
- Trim the leaves from the bottom two-thirds of the stem and add five to six cuttings to the base of the bottom leaves in gritty, cutting compost pots.
- Put the pots in a propagator or a plastic bag and place them somewhere with adequate light but not direct sunlight.
The cuttings should then root in two or three weeks, then you can pot them up individually and grow on them.
Petunia Pests or Diseases
Petunias can be infested by aphids and slugs, though they don’t get very serious insect or disease pests.
To help prevent disease, avoid getting the flowers and foliage wet when watering.
Suggested Petunia Uses
They can be used for hanging baskets, color masses, containers, borders, or as a seasonal groundcover.