Petunia seeds often fail to germinate because they are planted too deep in the soil. Read more about gardeners' tips for growing good seedlings.
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You need to spread the seeds on the surface of the soil and spray them with a little water from a spray bottle. The seeds will sink into the soil. Of course, after this method of planting, you cannot water them at first.
Petunias are very small, so they can be easily damaged by overwatering. Here's a simple tip: water with a syringe so as not to overwater the soil. Excessive moisture will cause the seedlings to rot.
As soon as you see 6 true leaves, you need to pinch the seedlings. You can do this with your fingers or scissors. By following all the rules, you will be able to grow beautiful petunia seedlings.