Fennel extract and preparation method thereof, and application of fennel extract in controlling growth of duckweeds

The invention discloses a fennel extract and a preparation method thereof, and application of the fennel extract in controlling the growth of duckweeds, and relates to the field of water protection. The method comprises the following step: subjecting fresh fennel stems and leaves to soaking extraction so as to obtain the fennel extract. The fennel extract provided by the invention is adopted to control the growth of the duckweeds or kill the duckweeds, has the advantages of greenness, environmental protection, harmlessness to human and livestock, etc., and has extensive application prospects.