Sweet fennel's natural range spans Central and Southeastern Europe, as well as parts of the Middle East and South Asia, flourishing with a preference for dry soils near the sea. Now, sweet fennel is cultivated and has naturalized in regions across all continents, indicating a broad distribution due to its versatility and adaptability. In certain areas, sweet fennel is sometimes thought to be an assertive grower, potentially affecting native flora, notably in parts of South America, Oceania, and Africa, where its presence is more recent. Despite this, sweet fennel remains a staple in various climates due to its cultivation for diverse utilitarian purposes.

Sweet fennel is toxic to cats and dogs. Ingesting the sap or juice of sweet fennel can cause poisoning, leading to symptoms like vomiting, diarrhea, and weakness. Immediate veterinary care is crucial if ingestion is suspected. Prevent pets' access to sweet fennel to avoid potential poisoning and ensure their safety. Seek professional help if any signs of distress are observed.