Here are some tips to help you grow sunflowers. 
- Water your sunflower seed start container every morning to keep the soil and sprouting seed moist.
- Once the sunflower sprout reaches a height of about 4 inches, transplant it directly into the soil. Sunflowers have long tap roots, so they don’t grow well in containers.
- Choose a spot that gets direct sunlight at least 6-8 hours each day.
- Give your sunflower plenty of water every morning, watering at the base of the plant. Try to avoid splashing water onto the leaves as excess moisture can cause powdery mildew and interfere with the growth of the plant.
- As the sunflower reaches its maximum height, it will begin to droop at the head. When petals fall off, the center florets dry up and the seed kernels begin to swell. At this stage, it’s best to cover your flower head with a mesh onion bag or loose burlap or paper bag. This keeps birds from eating your seeds.
- Cut the stalks at the base when the ripened seeds develop a hard shell. If you plan to eat your sunflower seeds or preserve them for your bird feeder, wait until the seeds are completely dry; then remove them by hand or by rubbing them over wire mesh into a basket. Store in tightly closed containers to maintain freshness and keep rodents away.
Would you like a more in-depth post on growing sunflowers? Here it is — compliments of Peter Weeks from The Daily Gardener. Mahalo!