How to Grow a Giant Sunflower

Prepare a spot that is 2 feet wide and 3 feet deep for each sunflower plant, placing them in full sun and using a rotary tiller. Remove the loosened soil from the planting hole and place it into a wheelbarrow, using a shovel. Discard all rocks and weeds from the soil in the wheelbarrow.

Add aged manure to the wheelbarrow soil at a ratio of at least 1 part manure to 2 parts soil. Use a garden fork to mix the manure evenly into the soil to add nutrients and improve the soil's texture for better drainage.

Incorporate 1 to 2 tbsp. of a slow-release, mineral fertilizer into the blended soil. Common slow-release fertilizers sell in granule form, which releases small traces of fertilizer as the soil receives water.

Fill the planting hole with the blended soil until full. If you have extra soil that will not fit back into the hole, use it for other plantings around your garden.

Sow five giant sunflower seeds 1 inch under the surface of the soil, spaced 6 inches apart, when outside day and night temperatures rise above 50 degrees Fahrenheit.

Cover the giant sunflower seeds with a thin layer of hay. Use weed-free hay if available. The hay will help to protect the sunflower seedlings from hungry snails and birds.

Continue to water the growing giant sunflower seedlings regularly to provide them with a moist soil. Feed the giant sunflowers a diluted mix of liquid fertilizer each week, referring to complete instructions since different products require dilution and application methods differently.

Thin the giant sunflower seedlings down to the three strongest stems when they grow 3 inches tall, using kitchen shears at the soil line. Repeat this thinning process again when the sunflower seedlings grow to be 12 inches tall, leaving the two strongest plants growing. Thin the last two sunflower plants down to the strongest sunflower when they reach 24 inches in height.

Protect the giant sunflower seeds from hungry birds by covering the head of the sunflower with nylon stocking.

Cut the giant sunflower seed head off the main stem with a knife when the yellow petals have dropped and the back of the head has turned yellowish-brown. Hang the head upside down on a porch, garage or other dark location until the seeds have dried and begin to fall.