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.
The flowers came in shades of pinks and purples, mostly, yet some flowers bloomed in a yellowish white hue. So beautiful!
I ended up having three of four trays of these petunias the first year, when I only intended 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 intended again to have only 72 plants, with some extra not knowing if my home saved seeds would grow. They all grew. All of them, giving me over 300 petunia plants.
Petunia Varieties
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. Lace Veil has white flowers, with a crinkled edge, along with a yellow center that gradients out into the white blossom. 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.
https://www.rareseeds.com/catalogsearch/result/?q=petunia
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. These seeds are more expensive, but they are so unique with their array of colors and the double blooms. Worth it to try.
When to Start Indoors?
Petunias take about 8 weeks before the average last frost to start indoors. This doesn’t mean that they cannot go outside in cooler temperatures before then. To have them in bloom earlier, such as in a hanging basket ready to go, plan when you want to set them outdoors, and start 8 weeks before that.
Starting indoors from seeds will provide a very viable plant. I find that most plants started from seed grow so much larger than from cuttings, which is what most plants from a nursery start from.
Petunia Seeds
Petunia seeds are some of the smallest seeds. When planting small seeds, sprinkle them on top of the soil. Majority of the small seeds from any flower needs light to germinate. Petunias do need light for germination, as well as a warm moist environment. Using a humidity dome is a must, and using a heat mat is recommended. It may take longer to germinate without a heat mat.
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.
Petunias need to be surface-sown, meaning just sprinkle the seeds on top of the soil medium, and the provide 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. Gently sprinkle the petunia seeds across the soil, or you can use a toothpick to place one or two seeds in each cell. I love the quicker speed of the sprinkling method, and when I did use a toothpick with saliva for petunia seeds, I still ended up with 10 seeds per cell! If I do end up with 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 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
Caring for Petunia Seedlings
Petunias germinate rather quickly when having light, heating mat, humidity dome, and good watering. If they have not germinated within 14 days, the seeds most likely will not germinate. The seed was either bad, or maybe something was not followed.
My petunias germinated like crazy this year. The seed was home saved seeds from an heirloom petunia, originally from Baker Creek. If the newly germinated petunias have stems that are long, sorta spinly-like, that’s okay. The seeds were surfaced sown, so they start where the seed was, and then develop roots from there.
Thinning Petunia Seedlings
I recommend thinning petunia seedlings before they reach their true leave stage, but after waiting until they have grown some roots. I’ve found that thinning by pulling out all the seedlings, separating them, and then potting them up in different containers is best done when the plants are smaller. When they are so much larger, they wilt upon transplanting, and some may have come root bound if they were in a cell with 10 other plants. Those 10 plants may not be as tall as other petunias since they have been competing for nutrients, space, and light.
Petunia Low Temperatures
With having multiple trays of petunias growing and less space available underneath grow lights, I needed to move some more plants out into the unheated greenhouse. The cool flowers were already outside in the greenhouse for an early Spring planting. With needing more room, I needed to decide what else I could store out there.
With having some cooler night temperatures down into the high-20’s or the low-30s, whatever plants were in the greenhouse needed to be able to withstand those cooler temperatures. If I had zinnias in this unheated greenhouse over those nights, the zinnias would not have made it.
Petunias thrive in night time temperatures between 55- and 65-degrees Fahrenheit. Yet, they can survive much lower temperatures down to 39- and 40-degrees Fahrenheit. In my unheated greenhouse, on those cooler nights, my petunias had the protection of the greenhouse, and they had the protection of a frost cloth or layer of plastic.
Why Grow Petunias from Seed?
I love buying petunias from local greenhouses. I still plant to buy some petunias this spring, preferably the Proven Winner brand offered at some of the local Amish greenhouses in my Western PA area.
Although I love all petunias, growing petunias from seed brings a sense of excitement for seeing a favorite flower grow and develop throughout the season. From seed to seed. After that first growing season where I did not have much success, it always excites me to see cells filled with countless petunia seeds germinating. Then they keep growing, and keep needing to be potted up. Blooming starts, and although I love to keep petunias in the landscape, I can’t help but cut a few of the stems for some arrangements.
Although beautiful, the petunias at local greenhouses and garden centers can become expensive. When companion planting petunias with the vegetable garden, many are needed to get the job done. Starting petunias from seeds is going to be cheaper than buying $3-$6 plants of each to companion plant with 100-some beans.
Lastly, have you even checked some of the seed packets for petunias? The one variety I am growing this year comes from Burpee, and it is double-bloom. I’ve never seen petunias like this before, even though I’ve had similar double-bloom petunias through Proven Winners. Being able to start petunias from seed is having the freedom to choose unique varieties not available in stores.
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