Petunias are one of the most popular annual flowers for both containers and garden beds. Prized for their wide range of gorgeous colors and ability to bloom continuously all season, petunias add a vibrant splash of color to outdoor spaces. With proper petunia care and by selecting suitable varieties, anyone can grow thriving, eye-catching petunias at home.
This comprehensive guide will walk you through how to successfully grow petunias in your garden or containers. We’ll cover choosing the right petunia types and colors, preparing the soil, planting, watering, fertilizing, deadheading spent blooms, controlling pests and diseases, overwintering, and saving seeds. Follow these tips to keep your petunias healthy, encourage lush flowers, and enjoy their beauty all season long.
Selecting the Best Petunia Varieties
Petunias come in a diverse range of varieties to suit different growing needs:
Grandiflora: Large, showy, ruffled blooms on mounding plants. Great for garden beds and borders. Flower size ranges from 3-5 inches. Popular varieties include ‘Mitchell’, ‘Ultra Red’, and ‘Pink Wave’.
Multiflora: Abundant smaller 1-2 inch flowers on compact, dense plants. Perfect for containers. Try ‘Celebrity Pink Morn’, ‘Dreams Red’, or ‘Primetime Blue’.
Spreading: Low, trailing plants that spread as groundcovers. Nice cascading from hanging baskets. ‘Easy Wave Red’ and ‘Shock Wave Coconut’ are good choices.
Wave: Vigorous, spreading plants with cascading flowers. Thrive in containers and baskets. Look for ‘Tidal Wave Silver’ and ‘Blue Wave’.
Supertunia: Bred for weather resistance and continuous blooming. Excellent garden performance. Try ‘Royal Velvet’ or ‘Bordeaux’.
Consider factors like mature plant size, growth habit, and intended use when selecting petunia varieties. Visit local nurseries to see colors and habits in person.
Choosing Complementary Petunia Colors
Petunias come in a stunning range of solid, veined, and multicolored blooms. Choose colors that create attractive combos:
Bold brights like red, orange, hot pink provide striking contrast against green foliage.
Cool pastels like purple, pink, light blue complement each other in soothing displays.
Darker colors like purple hold up better in full sun locations.
Multicolored varieties like ‘Papaya’ add depth and interest to plantings and containers.
Order seeds or purchase starter plants of your favorite petunia colors. Group complementary hues together for impact.
Preparing the Soil
Petunias need well-drained, nutrient-rich soil. Here’s how to prepare the ideal growing medium:
Loosen soil and mix in 2-4 inches of organic compost or well-rotted manure. This improves drainage and adds nutrients.
Test soil pH. Petunias prefer a slightly acidic pH between 6.0-6.5. Adjust if needed by mixing in elemental sulfur.
Work compost thoroughly into the top 6 inches of soil. Level and rake smooth to create a uniform growing bed.
For containers, use a quality potting mix blended for flowers and vegetables. Or make your own blend.
Proper soil prep establishes the foundation for healthy petunia roots and vigorous growth.
Improving Drainage
Excess moisture is problematic for petunias. Improve drainage by:
Adding organic material like compost, peat moss, or coconut coir to soil to lighten texture.
Installing raised garden beds to elevate plants above compacted soil. Frame with wood, bricks, or stones.
Creating mounded planting beds to facilitate drainage. Make mounds 6-12 inches high.
Adding perlite, vermiculite, sand or small gravel to potting mixes to improve porosity.
Ensuring containers have several 1/4 inch drainage holes. Elevate pots above saucers.
Proper drainage prevents wet soil that leads to root rot and other petunia problems.
Planting Petunias
Once soils warm to 60°F in late spring, it’s time to plant petunias outdoors:
Where to Plant
In full sun locations with at least 6 hours of direct sunlight daily. Morning sun is ideal.
In protected spots away from strong winds, which can damage tender plants. Use windbreaks if needed.
After the last expected frost date when nighttime temperatures will remain above 50°F consistently.
Transplanting Seedlings
Harden off seedlings for 7-10 days by slowly exposing them to outdoor conditions. Bring inside at night.
Dig holes the same depth as seedling root balls. Gently remove from pots and place in holes.
Backfill soil around roots and water thoroughly to settle soil and eliminate air pockets.
Planting Seeds Outdoors
Sow seeds 1/4-1/2 inch deep and 12 inches apart in prepared soil after frost danger has passed.
Water gently to moisten soil after planting. Keep soil evenly moist until seeds germinate in 5-15 days.
Thin seedlings to final spacing of 6-12 inches apart depending on variety when 2-3 true leaves emerge.
Caring for Petunias
Give your petunias the proper care to fuel lush, vibrant blooms all season:
Watering
Water early in the day to allow leaves time to dry before nightfall to prevent disease.
Check soil moisture daily. Water when the top few inches become dry. Flowering plants need 1-1.5 inches of water weekly.
Water thoroughly until soil is moistened to the entire root zone. Proper watering encourages deep roots.
Adjust frequency based on weather, plant size, and soil type. Avoid both wilting and saturated soil.
Fertilizing
Use bloom-boosting fertilizer like 15-30-15 twice per month during peak growing season for abundant flowers.
For containers, apply a balanced soluble fertilizer monthly according to label rates.
Avoid over-fertilizing which causes excess foliage growth at the expense of flowering.
Deadheading
Pinch off spent blooms just above a set of healthy leaves using your fingertips.
Deadhead faded flowers daily to promote continuous blooming all season long.
Remove damaged, diseased or insect-infested growths as soon as noticed to improve plant health.
Pest and Disease Control
Inspect plants daily and take prompt action at first signs of pests like aphids, thrips or spider mites.
Remove and destroy seriously infested plants to prevent spreading.
Use insecticidal soap, neem oil or appropriate organic remedies for minor infestations.
Improve air circulation between plants and avoid wetting foliage to prevent powdery mildew and other fungal diseases.
Overwintering Petunias
Petunias are generally grown as annuals in most regions, but you can overwinter them as perennials in mild climates:
Take cuttings from vigorous, healthy plants in late summer. Root cuttings in sterile potting mix.
Transplant rooted cuttings to containers and move to a sheltered spot outdoors once night temperatures drop below 40°F.
Water sparingly over winter. Provide bright light from a south facing window if overwintering indoors.
In spring, prune plants back by one third and repot into fresh mix if rootbound. Grow on in good light.
Harden off overwintered plants and transplant to the garden after the danger of frost has passed.
Saving Petunia Seeds
Preserve your favorite petunia varieties by collecting and saving seeds each season:
Allow chosen flower heads to remain after blooming finishes until the base of the flower dries and browns.
Gently crush dried flower heads over a plate to release small seeds. Discard pods.
Place seeds in an envelope or jar labeled with the petunia variety and date.
Store sealed containers in a cool, dry place like the refrigerator to maintain seed viability.
For best germination, sow saved seeds the following season. Discard unused seeds after 1 year.
Troubleshooting Common Petunia Problems
Even with proper care, issues can occasionally arise with petunias. Here are some common problems and how to resolve them:
Wilting Plants
Check soil moisture – wilting can indicate under watering. Water thoroughly if soil is dry.
Improve drainage if soil is soggy or roots are rotted. Move to drier location.
Give afternoon shade if wilting on hot days despite adequate soil moisture.
Leggy Growth
Increase sunlight exposure to 6+ hours of direct sun daily. Move to sunnier spot.
Pinch or snip off leggy stems just above a set of leaves to encourage bushier growth.
Use dwarf, naturally compact varieties suitable for partial shade if sunlight cannot be improved.
Few or No Flowers
Fertilize regularly with a bloom-boosting fertilizer every 2-3 weeks during growing season.
Deadhead spent blooms to encourage continuous flowering.
Provide more sunlight and avoid over-fertilizing with nitrogen. Excess nitrogen leads to foliage growth instead of flowers.
Powdery Mildew
Improve air circulation between plants to reduce humidity levels.
Avoid wetting foliage when watering and water early in the day so leaves dry quickly.
Remove and destroy severely infected plants to prevent spreading.
Use fungicides like neem oil or sulfur for minor infections if organic methods are ineffective.
Designing With Petunias
A few simple design principles can help you use petunias to maximum effect:
Use trailing types in hanging baskets and containers to showcase cascading flowers.
Plant bold brights en masse for high impact color.
Edge garden beds and borders with low spreading varieties.
Combine colors for dramatic contrast like purple and yellow or red and white.
Use petunias of the same color but different shapes for texture.
Interplant annuals like marigolds, zinnias or salvias to create mixed plantings.
Plant in clusters or drifts of 3, 5, or 7 plants for greater visual appeal.
Let your imagination run wild when planning out your petunia garden. Their versatile forms, colors, and adaptability lend themselves to virtually endless possibilities!
Enjoying Petunias
Beyond their outstanding beauty, there are many ways to enjoy growing petunias:
Their profuse blooms attract pollinators like bees, butterflies, and hummingbirds to the garden.
Use cut flowers to create vivid bouquets and arrangements for indoors.
Preserve blossoms by drying them to retain their shape and color. Hang upside down in a dry location out of direct sun.
Make paint or infuse oil and vinegar with petunia blooms to add color.
Capture their ephemeral beauty through photography and painting.
Let their prolific flowers inspire creativity and gratitude for nature’s bounty.
Get Colourful and Creative With Petunias
With proper selection, planting, petunia care and maintenance, petunias will flourish and blanket your garden or containers with vivid, lasting color from spring until frost. Just be sure to provide these beautiful bloomers with their preferred growing conditions and your green thumb will shine through!
