Hops are the female flower clusters (commonly called seed cones or strobiles), of a hop species, Humulus lupulus. They are used primarily as a flavoring and stability agent in beer, to which they impart a bitter, tangy flavor, though hops are also used for various purposes in other beverages and herbal medicine. Hops were cultivated continuously around the 8th or 9th century AD in Bohemian gardens in the Hallertau district of Bavaria and other parts of Europe. However, the first documented use of hops in beer as a bittering agent is from the 11th century. Before this period, brewers used a wide variety of bitter herbs and flowers, including dandelion, burdock root, marigold, horehound (the German name for horehound means "mountain hops"), ground ivy, and heather. Hops are used extensively in brewing for their many purported benefits, including balancing the sweetness of the malt with bitterness, contributing a variety of desirable flavors and aromas, and having an antibiotic effect that favors the activity of brewer's yeast over less desirable microorganisms. Historically, traditional herb combinations for ales were believed to have been abandoned when ales made with hops were noticed to be less prone to spoilage.