''Lactuca muralis'', the wall lettuce, is a

perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

in the tribe

Cichorieae The Cichorieae (also called Lactuceae) are a tribe in the plant family Asteraceae that includes 93 genera, more than 1,600 sexually reproductive species and more than 7,000 apomictic species. They are found primarily in temperate regions of the E ...

within the family

Asteraceae Asteraceae () is a large family (biology), family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the Order (biology), order Asterales. The number of species in Asteraceae is rivaled only by the Orchi ...

. It is also referred to as ''Mycelis muralis''.Parnell, J. and Curtis, T. 2012. ''Webb's An Irish Flora''. Cork University Press. 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 in length. There are no disc flowers. ''Lactuca muralis'' grows about tall with the lower leaves

pinnate Pinnation (also called pennation) is the arrangement of feather-like or multi-divided features arising from both sides of a common axis. Pinnation occurs in biological morphology, in crystals, such as some forms of ice or metal crystals, and ...

ly toothed and clasping.

Description

''Lactuca muralis'' is slender, hairless herb growing from 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.Clapham, A.R., Tutin, T.G. and Warburg, E.F. 1968 ''Excursion Flora of the British Isles Second Edition''. Cambridge The upper leaves are stalkless, smaller and less lobed. All leaves are red tinged. The achenes are short beaked, spindle shaped and black. The pappus has simple white hairs, the inner longer than the outer. The flower heads are yellow, small with only 4–5 yellow ray florets. wide more or less, on branches 90 degrees to the main stem, in loose panicle.Webb, D.A., Parnell, J. and Doogue. D. 1996. ''An Irish Flora''. Dundalgan Press (W. Tempest) Ltd. It flowers from June until September. ''Lactuca muralis'' is similar to ''

Lactuca serriola ''Lactuca serriola'', also called prickly lettuce, milk thistle (not to be confused with '' Silybum marianum'', also called milk thistle), compass plant, and scarole, is an annual or biennial plant in the tribe Cichorieae within the family Aster ...

'' L. and ''

Lactuca virosa ''Lactuca virosa'' is a plant in the ''Lactuca'' (lettuce) genus, often ingested for its mild analgesic and sedative effects. It is related to common lettuce (''Lactuca sativa, L. sativa''), and is often called wild lettuce, bitter lettuce, lait ...

'' L. but clearly distinguished by having only 5 florets.

Taxonomy

The specific Latin epithet ''muralis'' is interpreted as 'growing on walls'.

Distribution and ecology

''Lactuca muralis'' is a native of Europe but has invaded shady roadsides, paths and logged areas of the

Pacific Northwest The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...

and New England It has become naturalized in parts of

Northern Ireland Northern Ireland ( ; ) is a Countries of the United Kingdom, part of the United Kingdom in the north-east of the island of Ireland. It has been #Descriptions, variously described as a country, province or region. Northern Ireland shares Repub ...

as long ago as 1913.Hackney, P. Ed. 1992. ''Stewart and Corry's Flora of the North-east of Ireland''. Institute of Irish Studies and The Queen's University of Belfast. (HB) It was first recorded in

The Burren The Burren ( ; ) is a karst/glaciokarst landscape centred in County Clare, on the west coast of Republic of Ireland, Ireland.

, where it is now frequent, in 1939. It can be found in woodlands, especially

Beech Beech (genus ''Fagus'') is a genus of deciduous trees in the family Fagaceae, native to subtropical (accessory forest element) and temperate (as dominant element of Mesophyte, mesophytic forests) Eurasia and North America. There are 14 accepted ...

. It is also found in calcareous soils, and walls.

References

* * {{Taxonbar, from1=Q15629257, from2=Q1546483 muralis Flora of Europe Plants described in 1753 Taxa named by Carl Linnaeus