Gardeners love the sunflower plant (Helianthus annus) for its giant yellow blossoms that tower in the air, sometimes to a height of 7 feet or more. They're very easy to grow in any garden, according to the University of Illinois. Instead of buying sunflower seeds from a garden store every year, save yourself money by harvesting seeds from your existing sunflower plant.
Grow sunflowers. Sunflowers thrive in full sun and can be planted as soon as the outside temperature has warmed to 46 degrees Fahrenheit, according to the University of Missouri. If you're growing more than one sunflower, space each plant apart by 2 feet, according to the University of Minnesota. Provide approximately 1 inch of water per week.
Wait for the sunflower's seeds to mature in the flower. Signs of maturity include dried or fallen flower petals, seeds with a black appearance, and the back of the flower taking on a brown hue, according to the University of Illinois.
Use a knife or pruning shears and cut off the flower head as soon as it exhibits all the aforementioned signs of maturity, but don't wait until the seeds are loose and dropping out of the flower. Leave 1 foot of stalk attached to the flower head.
Hang the flower head in a cool and dry room using twine or rope. Let the flower dry until the seeds are loose and fall easily when touched.
Collect the seeds. Hold the flower over a container. Rub the face of the flower with the palm of your hand. The seeds will drop into the container. Empty the seeds into a cloth bag and store them until you're ready to plant new sunflowers.