Answer: Sunflower seed hulls are somewhat allelopathic, meaning they may inhibit the growth of some other plants. A small quantity is unlikely to do harm. Creosote is thought to exude a toxic substance to inhibit the growth of nearby plants as a survival mechanism in the desert, where water and nutrients are scarce. However, I am not sure that there is research to back this up. I have many friends with creosote planted closely to other plants in their landscapes without ill effects. Also, some desert plant species actually use the creosote for sun protection in the desert such as tiny mammillaria cacti and Arizona queen of the night. Even the mighty saguaro often begins life beneath the protection of a creosote. So, I wouldn't worry about it in your landscape.
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