Q: For several years I had a bird feeder hanging over my St. Augustine grass. I used sunflower seed and I began to notice that the grass beneath the feeder had stopped growing. I now have an eight foot circle that is bare of grass.
A: It’s true that sunflower seeds inhibit the growth of some, but not all, plants growing nearby. I don’t know of any research that shows allelopathy of sunflower seed hulls towards St. Augustinegrass. A contributing factor could be the ground-feeding birds and rodents who constantly scratch under your feeder and damage grass plants by their frantic work. Consider using a seed guard that prevents bird food from falling to the ground.