Lactuca serriola (compass plant)

annual or biennial

place of origin: Europe

urban habitat: commonly found on roadsides, neglected residential and commercial landscapes, minimally maintained parks, abandoned fields, highway banks and medians, and pavement openings and cracks; drought tolerant but grows best in nutrient-rich soils.

ecological function: disturbance-adapted colonizer; can be used for phytoremediation in degraded urban landscapes by absorbing heavy metals and binding them to organic matter.

Native to south and central Europe, Lactuca serriola it is currently found throughout the US and Canada. The milky sap that exudes from all parts of this plant when broken contains lactucarium, which has a weak narcotic effect. The sap has been used medicinally for an array of ailments, including insomnia, anxiety, neuroses, hyperactivity, whooping cough and rheumatism. In traditional European medicine, it was used as a diuretic and to stimulate the flow of milk in nursing mothers and Ancient Greeks used its juice as remedy against eye ulcers. The Navajo used the plant ceremonially, indicating it was most likely introduced into North America with the arrival of Europeans. A homeopathic remedy is made from the plant for treatment of catarrh, swollen liver, and urinary tract ailments. Prickly Lettuce is a wild ancestor of cultivated lettuce and its young tender leaves can be consumed raw or cooked and eaten as an asparagus substitute. An edible oil can be obtained from its seed. The mature plant is mildly toxic. The oil is also used in making soap, paints and varnishes.