Lactuca serriola L.

By Rebecca Reaves, Native Plants of Arizona 2005

Common Names: Prickly Lettuce (2,5,6,10), Horse thistle, Milk thistle, Wild lettuce (3), Wild opium (3,8).

Family: Asteraceae (12,10)

Synonymy: Lactuca scariola (6,10), Lactuca scariola (10),Lactuca virosa(8).

Etymology: Lactuca comes from the Latin word latteus (lac), which means “milky or full of milk” referring to the milky substance found within the plant (4,7,9). The Latin term Lactuca also means lettuce (1). The Latin term serriola means “in ranks”(1).

Identification

Growth Form: Herbaceous annual or biennial two to seven feet in height with a many- branched inflorescence (5,8,10).

Roots: Large taproot (5).

Stem: The branched stems are rigid and held erect, they are found mostly smooth but may be found with hair around the base of the plant (6,8). Stems contain white milky sap (5,6,8).

Leaves: Lower alternate leaves can be up to 10 inches long and 3 inches wide while upper leaves are smaller (8). Leaves are grayish or bluish green dentate to coarsely lobed (it varies widely). Leaves are oblong to lance shaped and clasping at the bottom (1,2,5,6,8), with spiny-toothed margins and distinct spines along the bottom midrib of each leaf (2,6,8).

Inflorescence/Flower: The diskless flowers contain only yellow-toothed square-tipped ray flowers (6). Dandelion–like 6-13mm flower heads containing up to 24 rays (2). Flowers are on tops of branched stems and occur are arranged in open clusters (8).

Fruit: Fruits are dry and single seeded. They have white bristles, which aid in dispersal (2).

Similar species: Lactuca serriola can be distinguished from other species in the genus by the spiny midrib on the bottom of the leaves (10).

Ecology

Life History: Tall annual or biennial herbaceous plant (6,10,).

Native/Introduced: Native to Europe. Introduced into the United States and now naturalized throughout the U.S (2,10).

Photosynthetic pathway:

Phenology: In northern Arizona it starts flowering in June and continues to flower and make fruit until the first frosts in October (5).

Distribution: Found throughout Arizona, often associated with riparian areas at lower elevations. Found in forty-nine U.S. states excluding Alaska (1). Grows best from approximately eight thousand feet down to approximately 2500 feet in elevation (1). Grows in waste places, roadsides, old fields or pastures, and disturbed soils (2,5,8). This plant thrives in nutrient rich soils (2).

Uses: Can be used as a potherb and is best to harvest the leaves when young (3,5). Has been used for its sedative qualities. Egyptians have used the seeds to make culinary oil. The flowers can be chewed like gum (5).

References:

Arizona Ethnobotanical Research Association.2005 edition. An Annotated Catalog of the Native and Naturalized Flora of Arizona. AERA Flagstaff, Arizona.
Boreal Forest.2005. Lactuca serriola. World Wide Web online resource. http://www.borealforest.org/world/herbs_shrubs/prickly_lettuce.htm. Accessed on 11/21/05.
Coffey, Timothy. 1993. The history and folklore of North American Wildflowers. Facts on File Inc. New York, New York.
Coombes, Allen J. 1985. Dictionary of Plant Names. Timber press. Beaverton Oregon.
Duke, James A. 1992. Handbook of Edible Weeds. CRC Press Inc. Boca Raton, Florida.
Firefly Forest. 2005. Lactuca Serriola. World Wide Web online resource. http://www.fireflyforest.com/flowers/yellow/yellow86.html. Accessed 11/21/05.
Quattrocchi, Umberto. 2000. CRC Dictionary of Plant Names- Common Names, Scientific Names, Eponyms, Synonyms, and etymology. Volume II D-L. CRC press Inc. Boca Raton, Florida.
Sieves, A.F. 1930. The Herb Hunters Guide. Misc. Public. No 77.USDA Washington DC. World Wide Web online resource. http://www.hort.purdue.edu/newcrop/herbhunters/pricklylettuce.html. Accessed 11/21/05.
University of Notre Dame.2005. Latin Dictionary and Grammar Aide. World Wide Web online resource. http://catholic.archives.nd.edu/cgibin/lookup.pl?stem=lactuca&ending. Accessed 11/21/2005
USDA, NRCS. 2005. The PLANTS Database, Version 3.5 ( http://plants.usda.gov). Data compiled from various sources by Mark W. Skinner. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Lactuca serriola L. By Rebecca Reaves, Native Plants of Arizona 2005 Common Names: Prickly Lettuce (2,5,6,10), Horse thistle, Milk thistle, Wild lettuce (3), Wild opium (3,8). Family: Asteraceae (12,10) Synonymy: Lactuca scariola (6,10), Lactuca scariola (10),Lactuca virosa(8). Etymology: Lactuca comes from the Latin word latteus (lac), which means “milky or full of milk” referring to the milky substance found within the plant (4,7,9). The Latin term Lactuca also means lettuce (1). The Latin term serriola means “in ranks”(1). Identification Growth Form: Herbaceous annual or biennial two to seven feet in height with a many- branched inflorescence (5,8,10). Roots: Large taproot (5). Stem: The branched stems are rigid and held erect, they are found mostly smooth but may be found with hair around the base of the plant (6,8). Stems contain white milky sap (5,6,8). Leaves: Lower alternate leaves can be up to 10 inches long and 3 inches wide while upper leaves are smaller (8). Leaves are grayish or bluish green dentate to coarsely lobed (it varies widely). Leaves are oblong to lance shaped and clasping at the bottom (1,2,5,6,8), with spiny-toothed margins and distinct spines along the bottom midrib of each leaf (2,6,8). Inflorescence/Flower: The diskless flowers contain only yellow-toothed square-tipped ray flowers (6). Dandelion–like 6-13mm flower heads containing up to 24 rays (2). Flowers are on tops of branched stems and occur are arranged in open clusters (8). Fruit: Fruits are dry and single seeded. They have white bristles, which aid in dispersal (2). Similar species: Lactuca serriola can be distinguished from other species in the genus by the spiny midrib on the bottom of the leaves (10). Ecology Life History: Tall annual or biennial herbaceous plant (6,10,). Native/Introduced: Native to Europe. Introduced into the United States and now naturalized throughout the U.S (2,10). Photosynthetic pathway: Phenology: In northern Arizona it starts flowering in June and continues to flower and make fruit until the first frosts in October (5). Distribution: Found throughout Arizona, often associated with riparian areas at lower elevations. Found in forty-nine U.S. states excluding Alaska (1). Grows best from approximately eight thousand feet down to approximately 2500 feet in elevation (1). Grows in waste places, roadsides, old fields or pastures, and disturbed soils (2,5,8). This plant thrives in nutrient rich soils (2). Uses: Can be used as a potherb and is best to harvest the leaves when young (3,5). Has been used for its sedative qualities. Egyptians have used the seeds to make culinary oil. The flowers can be chewed like gum (5). References: Arizona Ethnobotanical Research Association.2005 edition. An Annotated Catalog of the Native and Naturalized Flora of Arizona. AERA Flagstaff, Arizona. Boreal Forest.2005. Lactuca serriola. World Wide Web online resource. http://www.borealforest.org/world/herbs_shrubs/prickly_lettuce.htm. Accessed on 11/21/05. Coffey, Timothy. 1993. The history and folklore of North American Wildflowers. Facts on File Inc. New York, New York. Coombes, Allen J. 1985. Dictionary of Plant Names. Timber press. Beaverton Oregon. Duke, James A. 1992. Handbook of Edible Weeds. CRC Press Inc. Boca Raton, Florida. Firefly Forest. 2005. Lactuca Serriola. World Wide Web online resource. http://www.fireflyforest.com/flowers/yellow/yellow86.html. Accessed 11/21/05. Quattrocchi, Umberto. 2000. CRC Dictionary of Plant Names- Common Names, Scientific Names, Eponyms, Synonyms, and etymology. Volume II D-L. CRC press Inc. Boca Raton, Florida. Sieves, A.F. 1930. The Herb Hunters Guide. Misc. Public. No 77.USDA Washington DC. World Wide Web online resource. http://www.hort.purdue.edu/newcrop/herbhunters/pricklylettuce.html. Accessed 11/21/05. University of Notre Dame.2005. Latin Dictionary and Grammar Aide. World Wide Web online resource. http://catholic.archives.nd.edu/cgibin/lookup.pl?stem=lactuca&ending. Accessed 11/21/2005 USDA, NRCS. 2005. The PLANTS Database, Version 3.5 ( http://plants.usda.gov). Data compiled from various sources by Mark W. Skinner. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.