The terms “prickly lettuce” and “wild lettuce” frequently lead to confusion, often used interchangeably by those exploring the natural world. “Wild lettuce” is a broad common name for various species within the Lactuca genus, which also includes cultivated lettuce. This article clarifies the distinctions between Lactuca serriola (Prickly Lettuce) and Lactuca virosa (Opium Lettuce), often the plant people seek when using the general term “wild lettuce.”
Prickly Lettuce Identification and Characteristics
Lactuca serriola, known as Prickly Lettuce or Compass Plant, is a common annual or biennial weed found in disturbed areas like roadsides and abandoned fields. It typically grows between one and five feet tall, sometimes reaching up to seven feet. A distinguishing feature is the presence of stiff prickles along the midrib on the underside of its leaves and on the leaf margins.
The leaves of L. serriola are alternate, often deeply lobed, and clasp the stem at their base. Its leaves tend to orient themselves vertically in a north-south plane, earning it the name “Compass Plant” and helping it manage sun exposure. When broken, a milky white sap exudes from the stems and leaves. The plant produces numerous small, pale yellow flowers, about one-quarter to one-half inch in diameter, which typically bloom from late spring to early summer.
Opium Lettuce The Often Confused “Wild Lettuce”
Lactuca virosa, often called Opium Lettuce, is frequently the species of interest due to its historical use. This biennial herb can grow considerably taller than its prickly counterpart, reaching heights of up to six or seven feet. Its stems are generally smooth and light green, sometimes displaying purplish spots or a purple flush.
The leaves of L. virosa are smoother and less prickly than those of L. serriola. When cut, it produces a milky white sap called lactucarium. This lactucarium has a bitter taste and earned the plant its “opium lettuce” moniker due to its perceived mild sedative and pain-relieving effects, once compared to opium. The plant contains compounds like lactucin and lactucopicrin, which contribute to these properties.
Distinguishing Between the Two Species
Differentiating between Lactuca serriola and Lactuca virosa involves observing key physical characteristics. The most reliable distinction is the presence of spines on the leaves. Lactuca serriola has distinct, stiff prickles along the midrib on the underside of its leaves and often on the leaf margins. In contrast, Lactuca virosa is notably less prickly, with smoother leaves.
Stem color also offers a clue: L. virosa often exhibits purplish-flushed or spotted stems, while L. serriola stems are typically green or reddish, sometimes with few bristles near the base. Additionally, L. serriola leaves uniquely orient themselves vertically in a north-south direction, a characteristic not found in L. virosa.
Safety and Responsible Foraging
Foraging for wild plants, including Lactuca species, requires extreme caution due to the potential for misidentification with other, possibly toxic, plants. Accurate identification is paramount before consumption. Even within the Lactuca genus, chemical composition and effects can vary.
Consuming wild-harvested plants carries inherent risks, as there are no regulated doses. Lactuca virosa can cause adverse effects, especially when ingested fresh or in excessive quantities. Reported symptoms include dilated pupils, dizziness, anxiety, urinary retention, and gastrointestinal issues. In severe cases, consumption has led to hospitalization. Wild lettuce can also induce sleepiness and may interact negatively with sedative medications, so consulting healthcare professionals before use is important for personal safety.