Lactuca virosa L. is a secondary wild relative of lettuce, L. sativa L. (USDA, ARS, National Genetic Resources Program 2010).

An endemic subspecies is recognized in Spain: L. virosa ssp. livida (Boiss. & Reut.) Ladero & A. Velasco.

European regional assessment: Data Deficient (DD)
EU 27 regional assessment: Data Deficient (DD)

Lactuca virosa is assessed as Data Deficient as there is currently insufficient information available to evaluate this species. Information about its precise native range, population size and trend is needed, as well as its in situ conservation status and potential threats.

L. virosa is native to central, southeastern and southwestern Europe, as well as to north Africa; it has become naturalized outside its native range in both of these regions (USDA, ARS, National Genetic Resources Program 2010).

Knowledge of the national distribution of this species in Europe is as follows:

• Portugal: north and central.
• Italy: widespread.
• France: widespread, but not recorded in the departments of Pas-de-Calais, Maine-et-Loire, Hauts-de-Seine, Eure-et-Loir, Cher, Haute-Saône and Territoire de Belfort in the northern half of the country (Association Tela Botanica 2000–2010).
• United Kingdom: widespread across the southern half of England, particularly to the east, with a patchier distribution to the north and in Scotland (Preston et al. 2002). Its distribution in Wales is particularly limited and it is only recorded in two localities in Northern Ireland (Preston et al. 2002).
  
• Germany: common but its origin is uncertain (R. Vögel pers. comm. 2010). 
  
• Croatia and Serbia: presence uncertain and if present, its origin is uncertain.
• Slovakia: found only as casual alien in Ivánka pri Nitre (Dostál and Červenka 1992).

This species is generally considered to be rare in central Europe (Lebeda et al. 2004); however, it is reported to be common in Italy, Sicily and Sardinia (D. Donnini pers. comm. 2010).

L. virosa is an annual to biennial herbaceous species which grows in ruderal habitats such as roadsides, embankments and grassy borders throughout most of its range. In Portugal, it grows in dry, sandy and rocky places. In the north of its range it can also be found on limestone, as well as on sand dunes (Feráková 1977, Lebeda et al. 2004). In Great Britain, it occurs in lowland habitats (coastal cliffs, inland rocky outcrops and sand dunes), but it prefers rank calcareous grassland, woodland margins, road banks, quarries, tracks and rough ground (Preston et al. 2002). It grows in lowland and sub-montane areas, with plants occasionally found at higher altitudes (e.g., 1,560 m in Switzerland) (Feráková 1977).

The threats to this species are unknown.

L. virosa is a secondary wild relative of and potential gene donor to lettuce, L. sativa. This species is also used for medicinal purposes (Lebeda et al. 2004) and is sometimes collected for salads.

L. virosa is listed as Vulnerable (VU) in Switzerland (Moser et al. 2002). The natural range of this species is receding and it is considered to be threatened in both Germany and Austria (Lebeda et al. 2004).

EURISCO reports 237 germplasm accessions of L. virosa held in European genebanks, 224 of which are reported to be of wild or weedy origin. Of the wild accessions, 104 originate from within Europe (EURISCO Catalogue 2010).

Research is needed to determine the native range of this species; particularly in central Europe.