The Wavy-leafed Soap Plant, Chlorogalum pomeridianum, is the commonest and most widely distributed of the Soap Plants, Soaproots or Amoles, which make up the genus Chlorogalum of flowering plants. It is found in most of California, apart from the Sierra Nevadas and the deserts, and also in south-western Oregon. It is occasionally known as the "wild potato", but given the plant's lack of either resemblance or relationship to the potato, this name is not recommended.

Like all the Soap Plants, the Wavy-leafed Soap Plant is a perennial that grows from a bulb, which is brown, between 7 and 15 cm in diameter, slightly elongated, and covered in thick, coarse fibres. The leaves grow from the base of the plant, and can be from 20 to 70 cm long and 6 to 25 mm wide. As the plant's name indicates, their edges are generally wavy, though this is not always particularly noticeable. The flowers are borne on a long stem, normally longer than the leaves, and are from 15 to 30mm long. The six petals (actually only three of them are petals in the technical sense; the other three are sepals) are up to 35mm long and curving. They are generally white but have a noticeable mid-vein which can be purple or green in colour. The six stamens are large and noticeable, and yellow or orange. The flowers are hermaphrodite. They open only in the late afternoon or evening, remaining open during the night but closing by the morning. Pollination is by evening- or night-flying insects.

The Wavy-leafed Soap Plant grows on rock bluffs, grasslands, chaparral, and in the more open woodlands.

Three varieties are recognised:

• Chlorogalum pomeridianum var. divaricatum, endemic to some coastal regions of California (the Central Coast and southern parts of the North Coast), and only found at elevations below about 100 metres.
• C. p. var. minus, found in the inner north and outer south Pacific Coast Ranges of California, and the San Francisco Bay Area. This variety has a less fibrous bulb than the others.
• C. p. var. pomeridianum, found throughout the range of the species.

The juices of the bulb contain saponins that form a lather when mixed with water, and both Native American people and early European settlers used the bulbs as a kind of soap; this is the origin of the plant's name. It was particularly used for washing hair, since it was held to be effective against dandruff. Extracts of the bulbs could also be used as a sealant or glue.

The young leaves can be used as food, but the saponins in the bulbs make these poisonous. However saponins are very poorly absorbed by the body and usually pass straight through, and in any case they can be destroyed by thorough cooking. The Miwok people roasted and ate the bulbs as a winter food. Saponins are much more toxic to some other animals than they are to humans. Fish are particularly susceptible, and the bulb juices were used to kill or stun them so they could be caught easily.

The bulbs also had various medicinal uses, both external (e.g. for making a poultice to be used as an antiseptic, or as a rub in cases of rheumatism) and internal (decoctions were used for a range of purposes, including as a diuretic, as a laxative and against stomach ache). The fibres surrounding the bulb were widely used, bound together, to make small brushes.

The basionym of the species was Scilla pomeridianum. It has also been known as Loathoe pomeridiana..

External links

• Species treatment from the Jepson Manual
• Species entry in Moerman's Native American Ethnobotany Database
• Palomar College site on Soap Lilies in California