Sunflowers are not poisonous to cats. All parts of sunflowers, including petals, leaves, and seeds, are non-toxic to cats. However, eating sunflowers can sometimes cause mild digestive upset like vomiting or diarrhea, especially if eaten in large amounts. The sunflower seed shells can pose a choking hazard or cause internal irritation if ingested, so they should be avoided. Also, salted or seasoned sunflower seeds are not safe for cats due to the added salt. Overall, sunflowers are safe for cats but should be kept out of reach to prevent overeating or choking risks.