The tendency to grow in and around walls in England gives wall lettuce (Lactuca muralis) both its common name and its species name (muralis from the Latin meaning “growing on walls”). Wall lettuce is native to Europe and is now naturalized in parts of North America – the Pacific Northwest through British Columbia and into Alaska, Idaho, Montana and portions of Eastern Canada and Northeastern United States.
Although some references describe wall lettuce as a perennial, most of the literature lists this hairless plant as an annual or biennial. Wall lettuce grows in moist forest glades, forest edges and disturbed areas such as roadsides and clearings at mid elevations. Although wall lettuce is not listed as a noxious weed, there are many botanists that believe it should be classified as a noxious weed.
One to several wall lettuce stems arise from a fibrous taproot. The genus name, Lactuca, is from the Latin “lacta” meaning “milk” and refers to the plant’s milky white sap.
Wall lettuce leaves are alternate and highly divided. The basal leaves and those on the lower stem are deeply lobed with a broad ivy-like terminal lobe and clasp the stem with a flange-like base. The leaves on the middle and upper stem are fewer in number, smaller and less lobed.
A member of the Aster Family, the flower head consists of five (some references say occasionally four) yellow ligulate flowers. Ligulate flowers are strap shaped, have five lobes and both fertile pistils and fertile stamens. There are no disc flowers in the wall lettuce flower head. The inflorescence is an open, airy cluster containing numerous flower heads.
Wall lettuce fruits are flattened achenes (a single dry seed) topped by a pappus of numerous whitish bristles. The achenes have a short beak and are black.
The leaves are edible and can be used raw in salads. To me the leaves and milky sap are bitter and not very palatable.
A synonym for L. muralis is Mycelis muralis with both names common in the literature.
This wall lettuce was growing along the Steep Canyon Trail in Silver Falls State Park (Marion County OR) and was photographed earlier this month.