After harvest, the flowers should be placed to finish drying, hanging the heads upside down in a warm, dry place. To prepare the seeds for eating, they should be fully dried. After they are fully dry, they should soak overnight in a strong salt water solution. Although a relatively easy flower to cultivate, there are still a few problems faced when growing sunflowers. Empty seeds are sterile seeds arranged in a circle around the flower head, and are due to a late season frost before pollination.
Aphids suck plant juices and in large numbers can cause stunting.
However, most all-purpose garden insecticides will kill them. Leaf mottle is caused by fungus which lives in the soil and affected plants cannot be cured. Leaf Mottle can sometimes be prevented by planting in another area the next year. This information is for educational purposes only. References to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned.