Alisma plantago-aquatica, also known as European water-plantain, common water-plantain or mad-dog weed, is a perennial flowering aquatic plant widespread across most of Europe and Asia, and apparently spread elsewhere in both the Old and New World.

Quick Facts Alisma plantago-aquatica, Conservation status ...

Alisma plantago-aquatica
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Monocots
Order:	Alismatales
Family:	Alismataceae
Genus:	Alisma
Species:	A. plantago-aquatica
Binomial name
Alisma plantago-aquatica L., 1753

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Alisma plantago-aquatica is a hairless plant that grows in shallow water, consists of a fibrous root, several basal long stemmed leaves 15–30 centimetres (6–12 inches) long, and a triangular stem up to 1 metre (3+1⁄2 feet) tall. It has branched inflorescence bearing numerous small flowers, 1 cm (1⁄2 in) across, with three round or slightly jagged, white or pale purple petals. The flowers open in the afternoon. There are three blunt green sepals and 6 stamens per flower. The carpels often exist as a flat single whorl.^[2] It flowers from June until August.^[3] The fruits appear as a ring of seeds inside each flower.^[3]

The word alisma is said to be a word of Celtic origin meaning "water", a reference to the habitat in which it grows. Early botanists named it after the Plantago because of the similarity of their leaves.^[5]

The species is widespread across most of Europe and Asia from Portugal and Morocco to Japan, Kamchatka and Vietnam. It is also regarded as native in northern and central Africa as far south as Tanzania, and in Australia.^[6] It is reportedly naturalized in southern Africa, New Zealand, Alaska, British Columbia, Washington state and Connecticut.^[7][8][9] Some sources maintain that the species is widespread across North America, but these reports appear to have been based on misidentified specimens.^[10] It is found on mud or in fresh waters.^[3]

The rootstocks contain starch and can be boiled or soaked to remove bitterness before eating. Aquatic plants in general should be cooked before consumption to kill parasites.^[11]

According to Flora of the U.S.S.R. (1934), "A powder prepared from dried roots is used in popular medicine as a cure for rabies and crushed leaves are used against mammary congestion; fresh leaves are employed in homeopathy. ... Since this species is often confounded or identified with others of the genus, the reported data may also refer to [A. orientale or A. lanceolatum]."^[12] A. plantago-aquatica is also known as mad-dog weed,^[13] as if it could be used to cure rabies, but should not be confused with Scutellaria lateriflora (mad-dog skullcap), which is also sometimes called mad-dog weed.

Alisma orientale is sometimes treated as a variety of this species (A. plantago-aquatica var. orientale).^[14][15] The rhizomes of A. orientale have been used as a traditional Chinese medicine, ze xie.^[16] However, it may have serious side effects or even toxic effects such as hepatotoxicity in patients with chronic hepatitis B.^[17]