Flower shopping with my mom and grandmother, petunias were a must to have in our gardens every year. Flower centers start these from plugs to then continue growing for their customers. Most petunias from the store are started from cuttings, which use an asexual method of reproducing the plant. With Baker Creek offering heirloom seeds, I grew their Balcony Mix Petunias from seed.
Most of the flowers were pink or purple, but some were a yellowish white color. So beautiful!.
Three of four trays of these petunias were full the first year, even though I had only planned to have 72 of them. The seeds are small, so when sprinkling, 10 or more seeds end up in each cell.
These seeds are also great to save, giving the same variety the following the season. For my second growing season, I planned to have only 72 plants, plus a few extra because I wasn’t sure if the seeds I had saved at home would grow. They all grew. All of them, giving me over 300 petunia plants.
Balcony Mix Petunias are classic petunias with their single blooms. They can be actually used as cut flowers for a short life flower. If not pinched, they grow one stem straight up. They work also great as bedding flowers in the landscape. If pinched, they will start branching out, keeping to a mounded shape. Saving seeds from these flowers will result in the same variety for the next season. These seeds can be ordered from Baker Creek Heirloom Seeds.
In 2023, Baker Creek has also expanded their petunia selection. If I could go and order more to start in time, I would have. I did order two more packets called Lace Veil and Superbissima Cerny’s Triump Mix. There are white flowers with a wavy edge on Lace Veil. The center is yellow and fades into the white flower. Superbissima Mix has a variety of colors and shades. I love how some have a darker color vine out into the lighter hue of the flower.
A variety that I have kept my eye on for years, I finally purchased it. Burpee’s charges shipping, and I never had enough seed packets to justify ordering from them. Then, I discovered their online store on Amazon. It costs more to buy these seeds, but the unique colors and double blooms make them worth it. Worth it to try.
With their wide array of colors and reliable performance, petunias are a classic summertime favorite. Most gardeners buy petunia transplants from nurseries in spring. However, starting petunias from seed indoors provides some advantages:
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Wider variety – Access unique or heirloom petunia varieties by seed
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Lower cost – Packets of seeds are cheaper than buying individual plants
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Stronger plants – Homegrown transplants develop large root systems and become very lush
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Longer bloom time – Earlier establishment from indoor starting extends flowering period
Growing petunias from seed is easy. Here is a complete step-by-step guide to successfully raise transplants indoors
When to Start Petunia Seeds Indoors
Petunia seeds should be started indoors 6-8 weeks before the anticipated outdoor planting date after your last spring frost. This gives adequate time for the seeds to germinate and seedlings to develop into short, stocky transplants ideal for transplanting.
In general, aim to sow petunia seeds in late February or March for an early to mid May garden planting time in most regions. Adjust timing accordingly based on your specific climate and last frost date.
Choosing Containers for Starting Seeds
To start petunia seedlings, you will need clean containers with drainage holes. Options include:
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Cell packs or trays – Most efficient use of space, come in various cell counts
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Peat or paper pots – Minimizes root disturbance at transplanting
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Planter flats – Allows even spacing between seedlings
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DIY trays/eggs cartons – Must punch holes yourself
Thoroughly clean used containers and sanitize by soaking in a 10% bleach solution for 10 minutes if reusing old trays or pots. This prevents any disease transmission.
Selecting an Indoor Seed Starting Mix
Use a sterile, soilless seed starting mix to start petunia seeds. This type of medium is lightweight and fine-textured, making it easy for delicate emerging seedlings to develop roots.
You can purchase premixed blends, or make your own by combining:
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Peat moss or coconut coir – Absorbs and retains moisture
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Perlite or vermiculite – Improves drainage and aeration
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Compost – Adds nutrients and organic matter
Avoid regular potting soil which is too heavy and may contain weed seeds or pathogens. Mix in a little extra perlite with starting mixes to further enhance drainage for petunias.
Filling Containers and Sowing Seeds
Here are step-by-step planting instructions when starting petunia seeds:
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Moisten seed starting mix until damp but not sopping wet. Let excess water drain.
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Gently firm the mix into cell trays or containers. Level off the surface.
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Very lightly sprinkle seeds onto the soil surface. Petunias need light to germinate so do not cover them.
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Gently press seeds into the mix using a block of wood or your fingers so they make good contact with the medium.
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Mist the seeded trays with water to further settle seeds. Do not saturate.
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Optional – Top dress seeded containers with a thin layer of vermiculite to retain moisture while germinating.
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Cover trays with plastic dome lids or plastic wrap to maintain humidity.
Caring for Seeded Trays
Once sown, petunia seed trays must be kept warm and moist continuously for the best germination rates:
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Temperature – Maintain a soil temperature of 70°F-75°F degrees. Use a heat mat if needed.
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Light – No light is needed until seeds sprout. Move to bright light immediately after germination.
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Moisture – Keep seeds consistently damp but not soaked. Mist softly when surface dries out.
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Humidity – High humidity is critical. Ensure trays are covered with domes or plastic wrap.
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Ventilation – Once sprouts emerge, remove domes and increase air circulation to prevent damping off disease.
When to Expect Germination
With proper care, petunia seeds will begin to germinate in 7-14 days. The timing varies based on soil temperature, seed freshness and variety.
Check trays daily once the 7 day mark hits. Gently stir the surface with your finger to expose any sprouts emerging underneath. Removing covers promptly prevents mold growth on tender seedlings once they emerge.
Caring for Petunia Seedlings
After germination, petunia seedlings require very bright light, cooler temperatures, adequate moisture and good air circulation:
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Lighting – Ensure 14-16 hours under grow lights or a sunny south window.
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Temperature – Move trays to a 60-70°F room. Avoid heat stress and prolong stretching.
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Watering – Allow starting mix to dry out slightly between waterings. Avoid standing water.
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Fertilizer – Begin mild fertilization once true leaves form. Use 1/4 strength soluble plant food.
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Spacing – Thin overcrowded groups to 1-2 seedlings per cell to avoid competition once they develop true leaves.
Hardening Off Petunia Transplants
Hardening off is the process of gradually acclimating indoor seedlings to outdoor conditions over 7-10 days. This toughens up the plants, prevents transplant shock and helps them establish quicker.
To harden off petunia transplants:
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Move pots outdoors to a sheltered, shaded spot for a few hours a day. Time duration can increase each day.
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Bring plants back indoors overnight until risk of frost has passed.
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Allow plants to experience partial sun, wind, temperature fluctuations and light rain.
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Reduce watering slightly to slow growth during the hardening off period.
Transplanting Petunias Outdoors
After the average last spring frost date has passed and seedlings are sufficiently hardened off, it is safe to transplant petunias into the garden. Here are some tips for a successful transition:
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Harden off plants for 7-10 days beforehand to prevent shock.
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Water seedlings thoroughly the day before and day of transplanting.
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Tease apart rootbound plants before planting.
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Dig holes the width of the root ball and plant at same depth as in pots.
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Use a starter fertilizer solution the day of planting to encourage establishment.
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Water transplants regularly for the first few weeks until roots expand into surrounding soil.
With proper care while starting seeds and hardening off, homegrown petunia transplants will thrive and reward you with vivid flowers all season long!
How to Plant Petunia Seeds?
- Pre-Moisten Soil
- Add Soil to Cells
- Sprinkle Petunia Seeds on Soil
- Place humidity dome on top
- Set on a Heat Mat & under Grow Light
Planting Petunia Seeds Indoors
I’ve messed up planting petunia seeds the first year I tried it. My mistake, well . I covered the seeds with soil. Most vegetables are planted at about ¼”. Make a small hole, insert seed, cover hole. Boom! Easy. Being used to planting vegetables, that’s what I did with petunias.
If you want to grow petunias, you just need to sprinkle the seeds on top of the soil and give them light. Petunias to seed off naturally, they just drop their seeds from their flower pod.
Using 72-cell trays, add pre-moistened soil medium to the cells. Spread the petunia seeds out gently in the soil, or you can use a toothpick to put one or two seeds in each cell. I like how the sprinkle method works faster, and even when I used saliva on a toothpick to plant petunia seeds, I still got 10 seeds per cell! If I get extra petunias, I’m all for it. I love these flowers that I’ll sell the extras or find a place to plant them for sure!.
Seedlings do need light for germination, as well as warmer temperatures. Place a humidity dome on top, which retains moisture, humidity, and a small amount of heat. Use a heat mat for additional warmth and a grow light for good lighting. Do not cover the seeds.
Seeds will germinate 7 to 14 days at 75-80 degree Fahrenheit.
✅ How to Grow Petunias from Seed – Start to Finish.
FAQ
Are petunias hard to start from seed?
What is the fastest way to germinate petunia seeds?
When should I start my petunia seeds indoors?
Do you soak petunia seeds before planting?
How to grow Petunia seeds?
A growing light system or greenhouse is ideal for large amounts of seedlings. If you are growing a few plants by seed, you can place them in your home’s windows for proper lighting. Start planting your petunia seeds by filling pots or cells with potting soil. Once you have gathered your materials, you can begin to plant your seeds.
How long does it take for petunias to germinate?
With that in mind, let’s start our germinating adventures… If you’re going to start petunias from seed, it’s best to start them indoors. They need a long time, over two months, to germinate and mature enough to transplant outside. Look at the last predicted frost date in your area and count back 10 or 11 weeks.
How do you plant a Petunia plant?
Plant the seeds: With any seeds, review the directions on the seed packet for proper planting. Petunia seed should be placed on top of the soil. If you use trays, you should only plant one seed per cell. Press the seeds firmly into the soil: Since petunias prefer light for germination, it’s unnecessary to cover the seed with soil.
How do you propagate Petunia seeds?
Sprinkle them gently on top of the soil, using only a small pinch of seeds. Petunia seed propagation only happens when they get the right amount of light. Don’t bother to buy special plant-growing light. Regular fluorescent lights work just as well. Place the plants on a shelf and hang the light directly above them.