What Plants Contain Lactucarium?

January 13, 2026 •

4 min read

Historically known as "lettuce opium," lactucarium is a milky latex produced by several species of plants in the genus Lactuca. While all plants in the lettuce family produce this substance to some degree, wild varieties are significantly more potent sources of lactucarium than the cultivated salad greens found in supermarkets. The concentration of this sap increases as the plant matures and begins to flower.

Quick Summary

Several wild lettuce species, particularly Lactuca virosa, produce lactucarium, a milky sap with historical sedative and analgesic properties. Other plants within the Lactuca genus, such as Lactuca serriola and Lactuca canadensis, also contain this latex, though typically in lower concentrations. This substance is most potent in flowering plants.

Key Points

Genus Lactuca: Lactucarium is a milky latex primarily found in wild species of the genus Lactuca, which includes various types of wild lettuce.
Lactuca virosa is Key: The most potent source of lactucarium is Lactuca virosa, also known as opium lettuce, which is the most concentrated among the lactuca species.
Other Wild Relatives: Other wild lettuce species like Lactuca serriola (prickly lettuce) and Lactuca canadensis (Canada wild lettuce) also produce lactucarium, but often in lesser amounts.
Potency Varies: The concentration of lactucarium increases as the plant matures, peaking during the flowering stage.
Active Compounds: The sedative and mild analgesic effects of lactucarium are attributed to compounds like lactucin and lactucopicrin.
Cultivated vs. Wild: Cultivated lettuce (Lactuca sativa) contains only trace amounts of lactucin and is not considered a viable source for lactucarium's medicinal effects.
Caution Advised: Despite historical use, there is limited modern scientific evidence on the effectiveness and safety of lactucarium for humans; potential side effects and overdose risks exist.

The Primary Source: Lactuca virosa

When discussing what plants contain lactucarium, the first and most notable is Lactuca virosa, commonly known as opium lettuce or bitter lettuce. This biennial herb is native to southern Europe but has been naturalized across many parts of the world. It is distinguished by its tall, often smooth, stem which can grow up to 6 feet in height and is sometimes spotted with purple. When the stem or leaves are damaged, a copious, milky-white sap, the lactucarium, is secreted. Historically, this dried latex was used as a sedative and pain-reliever, mimicking the effects of opium but without the same level of potency or addictive qualities. The concentration of active compounds, including lactucin and lactucopicrin, is highest when the plant is in flower.

Other Wild Lactuca Species with Lactucarium

While Lactuca virosa is the most famous for its potent sap, several other wild lettuce species also produce lactucarium. Their potency and flavor can vary, which is why proper identification is important for anyone interested in their properties. These relatives are all members of the Asteraceae (daisy) family and share the characteristic milky sap. The latex from these species can be collected and processed in a manner similar to L. virosa, though the yield and effect may differ.

Notable examples include:

Lactuca serriola (Prickly Lettuce): A widespread weed, this plant is known for its prickly midribs on the underside of its leaves and along its stem. It is native to Eurasia but has become naturalized globally. It contains lactucarium, but generally less than L. virosa. The young leaves are edible and less bitter.
Lactuca canadensis (Canada Wild Lettuce): Native to North America, this species grows tall with deeply lobed leaves. It contains lactucarium with similar sedative and anodyne properties. Concentrations are highest when the plant flowers.
Lactuca floridana (Woodland Lettuce): Another North American native, this wild lettuce is known for its blue or white ray florets. It also contains the characteristic milky sap and has been shown to contain the compound 11β,13-Dihydro-lactucin-8-O-acetate hemihydrate.
Lactuca biennis (Tall Blue Lettuce): This plant is distinguished by its potential to grow quite tall and its pale blue or whitish flowers. It is a potent source of lactucarium, with some anecdotal evidence suggesting it may be a strong sedative, though much is based on traditional use.

Cultivated Lettuce and Lactucarium

The story of lactucarium is not complete without mentioning the common cultivated lettuce, Lactuca sativa. While modern agricultural practices have bred out much of the bitterness and potency, even this variety contains trace amounts of lactucin, a compound also found in lactucarium. The amount is very low, however, and the plant lacks the concentrated medicinal properties of its wild relatives. Foragers note that wild lettuce is far more bitter, a testament to its higher concentration of these active compounds.

Lactucarium-Containing Plants Comparison


Feature	Lactuca virosa	Lactuca serriola	Lactuca canadensis	Lactuca sativa
Common Name(s)	Opium Lettuce, Bitter Lettuce, Great Lettuce	Prickly Lettuce, Compass Plant, Wild Lettuce	Canada Wild Lettuce, Tall Lettuce	Garden Lettuce, Cultivated Lettuce
Lactucarium Potency	High; traditionally considered the most potent source.	Moderate; less concentrated than L. virosa.	Moderate; has significant sedative properties.	Low; active compounds largely bred out.
Leaf Characteristics	Often less prickly; entire or serrate leaf margins.	Prickly midrib and leaf margins; often lobed.	Deeply lobed, lance-shaped leaves.	Varied, from loose-leaf to crisphead varieties.
Flower Color	Small, pale yellow flower heads.	Small, pale yellow flower heads.	Pale yellow flower heads.	Small, pale yellow flowers if allowed to bolt.
Primary Use	Historical medicinal use as a sedative and analgesic.	Young leaves can be eaten; minor medicinal use.	Edible leaves and stem when young; traditional medicine.	Culinary; food source.
Caution	Use with care; overdose can be toxic.	Use with caution; toxicity is possible in large amounts.	General caution for medicinal use; potency varies.	Generally safe for consumption.

The Active Components of Lactucarium

The sedative and analgesic effects associated with lactucarium are primarily attributed to a class of compounds called sesquiterpene lactones, particularly lactucin and lactucopicrin. These bitter substances act on the central nervous system, and research has shown they can produce mild pain-relieving effects. Lactucin, for example, has demonstrated analgesic effects comparable to ibuprofen in animal studies. It is important to remember that most studies are preclinical or historical, and the scientific community still requires more robust human studies to fully understand the effects and safety profile. Other plant compounds like flavonoids and coumarins have also been identified in these plants.

Conclusion

Lactucarium, the milky sap with sedative properties, is found predominantly in several wild species of the Lactuca genus. The most renowned source is Lactuca virosa, often called opium lettuce, which contains the highest concentration of the active compounds lactucin and lactucopicrin. Other species, including Lactuca serriola, Lactuca canadensis, and Lactuca biennis, also produce this latex, although in varying amounts. In contrast, commercially cultivated lettuce (Lactuca sativa) contains only negligible traces of these compounds. While historical and anecdotal evidence points to their use as a folk remedy for pain and anxiety, modern scientific research on their effectiveness in humans is limited. Due to the potential for side effects and lack of conclusive safety data, these plants should be used with extreme caution, and medical guidance is always advised before consumption. For more information on the history and chemical makeup of lactucarium, consult the detailed entry on Wikipedia.

Disclaimer: This article is for informational purposes only and is not intended to provide medical advice. Before using any plant for medicinal purposes, especially wild varieties, consult with a qualified healthcare professional. Improper identification or dosage could lead to adverse effects.

Frequently Asked Questions

Lactucarium is a milky-white, bitter latex fluid secreted by several species of lettuce, particularly wild varieties. Historically, it was used as a sedative and analgesic due to its mild pain-relieving properties, earning it the nickname "lettuce opium".

Cultivated garden lettuce (Lactuca sativa) contains only trace amounts of the compounds found in lactucarium. These have been largely bred out for commercial production, meaning regular lettuce is not a source of medicinal lactucarium.

Lactuca virosa, commonly known as opium lettuce or bitter lettuce, is generally considered to have the highest concentration of lactucarium among the Lactuca species.

While lactucarium has similar sedative and analgesic properties to opium, its effects are significantly milder. It has historically been promoted as a less potent and non-addictive alternative, but it is not a direct substitute.

Historically, lactucarium was harvested by making small cuts in the flowering stems of the plant and collecting the milky exudate. The substance is then dried until it forms a hard, brown resin-like material.

Consuming wild lettuce for medicinal purposes carries risks. Side effects, particularly with large doses, can include dizziness, anxiety, and vomiting. Research on safety and effectiveness in humans is limited, and expert medical advice should always be sought before use.

The primary active compounds are sesquiterpene lactones called lactucin and lactucopicrin. These compounds have been shown to have sedative and analgesic effects in animal studies, though more human research is needed.