Lactuca muralis, the wall lettuce, is a perennial flowering plant in the tribe Cichorieae within the family Asteraceae, also referred to as Mycelis muralis.[1] [2]
Its chief characteristic is its open airy clumps of yellow flowers. Each "flower" is actually a composite flower, consisting of 4–5 petal-like flowers (strap or ray flowers), each approximately 5– in length. There are no disc flowers. Lactuca muralis grows about 2- tall with the lower leaves pinnately toothed and clasping.
Lactuca muralis is slender, hairless herb[1] growing from 25to tall. It often has purplish stems, and exudes a milky juice.
The lower leaves are lyre shaped, pinnate shaped. The lobes are triangular in shape, the terminal lobe being the largest.[3] The upper leaves are stalkless, smaller and less lobed. All leaves are red tinged.[4]
The achenes are short beaked, spindle shaped and black. The pappus has simple white hairs,[1] the inner longer than the outer.
The flower heads are yellow, small with only 4–5 yellow ray florets.[5] [1] 1frac=4NaNfrac=4 wide more or less, on branches 90 degrees to the main stem, in loose panicle.[6] It flowers from June until September.[7]
Lactuca muralis is similar to Lactuca serriola L. and Lactuca virosa L. but clearly distinguished by having only 5 florets.[8]
The specific Latin epithet muralis is interpreted as 'growing on walls'.[9]
Lactuca muralis is a native of Europe but has invaded shady roadsides, paths and logged areas of the Pacific Northwest[10] and New England[11] It has become naturalized in parts of Northern Ireland as long ago as 1913.[12] It was first recorded in The Burren, where it is now frequent, in 1939.[13]
It can be found in woodlands, especially Beech.[6] It is also found in calcareous soils, and walls.