Lisse, gemeente (municipality), western Netherlands. It lies in the centre of the flower fields between Haarlem and Leiden. With Hillegom, it is one of the two great commercial centres of the Netherlands’ bulb-growing district. It is also the site of the State Bulb School and Laboratory. The annual flower exhibition (March to May; started in 1950), held on a former country estate around the 17th-century De Keukenhof Castle, consists of gardens covering 65 acres (26 hectares). Pop. (2007 est.) 21,975.