Whether you are growing ornamental or tall giant varieties or growing the sunflowers for seed production, starting from seed is an inexpensive way to add this bright and cheerful flower to the garden. Sunflowers are a summer annual, requiring warm temperatures and lots of sun to thrive. They bloom throughout summer and into fall. The edible seed varieties are dried and the seeds harvested for eating or for use as winter bird feed. Planting and growing from seeds is less expensive than growing from purchased seedlings.
Prepare a well-drained, full-sun garden bed for planting once all danger of frost has passed in spring. Lay a 2- to 3-inch layer of compost over the bed and till it into the top 6 inches of soil to aid drainage and add nutrients to the area.
Sow sunflower seeds 1/2 inch deep for shorter varieties and 1 inch deep for giant varieties. Space short and regular sunflowers 1 to 2 feet apart in rows that are 3 feet apart. Space giant sunflowers 3 feet apart in rows that are 4 feet apart.
Lay a piece of screen mesh or bird netting over the planting bed after sowing. Animals and birds dig up seeds from the garden bed if they are not protected. Remove the screen once the seeds sprout.
Water the bed deeply one to two times a week, soaking the soil until it feels moist to a 6-inch depth when you stick a trowel into it. Lay a 2-inch layer of mulch over the bed once the seedlings are 5 inches tall to help preserve soil moisture between watering.
Weed as necessary by hand pulling the weeds as they become visible. Mulching also helps prevent weeds, so weeding once every two weeks should be sufficient.