The short answer is 6 weeks before the last frost. I just started to grow my sunflower babies last week and I live in New Jersey 7b. If you want to plant the seeds directly in soil, I would say the best time to plant sunflower seeds is after the last frost in your area, when the soil has warmed up to at least 50°F (10°C). The reason that I recommend start 6 weeks indoor is because that it significantly extend the blooming time of your beautiful sunflowers.
Sunflowers are sensitive to cold, so it's important to wait until the risk of frost has passed to ensure successful transplantation and growth. If you're unsure about your local frost dates, you can check with a local gardening center or agricultural extension office for guidance.
Sunflower is one of the easiest flower to grow, I tried to plant them from seeds last year and it was a big success, very happy with the results. Here is a photo my husband standing with my giant sunflower. My husband is 6 feet, so you got the picture.
One fun fact I learned from Epic Gardening is that the sunflower is always facing east. So keep that in mind when you are planting your sunflower :)
You don’t have to soak the sun flower seed to plant it, but make sure the soil is wet enough. One last thing, when you’re ready to plant your sunflower seeds, just make sure all the seeds need to be pointed down.
