Answer: I have also heard that sunflowers inhibit plant growth, but have yet to see scientific evidence of this. I think a few other factors may be effecting your daffodils. Do they get plenty of sun? Are they well fertilized and in well drained soil? If you had "tons" of sunflower seed hulls I can see that they could bury the daffodils so they wouldn't emerge. I'd say rake up the hulls, compost them and plant whatever you want in that area. Just move the daffodils becaise it sounds like it's not a good spot for them with or without sunflower seed hulls.
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