Like many types of flowers, sunflowers can be grown both indoors and outdoors. If you want to get an early start on the growing season, you can begin sunflowers inside and move them outdoors once spring is in full bloom. The trick is to transplant sunflowers early, while they are still small.
If you want to start sunflowers indoors, plant seeds in separate compartments in a seeding tray. Fill the tray with potting mix, plant each seed so that about 1/2 inch of the mix covers the top of the seed, and water the soil until moist. Keep the soil in the tray moist and the temperature of the soil between 65 to 75 degrees, and green should appear above the soil in about a week.
When to Transplant
When sunflower seedlings reach 4 to 5 inches in height, you should transplant them if the weather outside is favorable. Like other flowers, sunflowers should not be transplanted outdoors until the chance of an overnight frost has passed for the season. Since letting a sunflower grow any taller than a few inches before transplant can weaken the structure of the plant, try not to start your sunflower plantings until late enough in the spring that you can transplant the sunflowers as soon as they reach the correct height.
Choose a location in your lawn that gets at least 6 hours of daily sunlight to transplant sunflower seedlings into. Dig a hole for each sunflower seedling from the seeding tray, keeping approximately 1-foot spacing between holes if you want the sunflowers to grow to full size. Transplant the strongest seedlings from the seeding tray to get the sturdiest sunflower crop.
Caring for Transplants
Once you transplant sunflowers outdoors, care of the plants is simple. Sunflowers require only a couple of main ingredients to thrive throughout summer. As long as the sunflowers receive full sun for at least 6 hours per day, though more is better, and adequate water, the plants can grow without any additional tending. In the absence of rain, water sunflowers at least once per week, increasing the watering schedule if the flowers begin to wilt.