Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Lactuca floridana
(woodland lettuce)

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Datasheet

Lactuca floridana (woodland lettuce)

Summary

  • Last modified
  • 27 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Lactuca floridana
  • Preferred Common Name
  • woodland lettuce
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • L. floridana is a weedy lettuce which can grow to almost 2 metres tall (Randall, 2012), locally common in disturbe...

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Identity

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Preferred Scientific Name

  • Lactuca floridana (L.) Gaertn.

Preferred Common Name

  • woodland lettuce

Other Scientific Names

  • Cicerbita floridana (L.) Wallr.
  • Cicerbita villosa (Jacq.) Beauverd
  • Lactuca floridana forma leucantha Fernald
  • Lactuca floridana var. villosa (Jacq.) Cronquist
  • Lactuca villosa Jacq.
  • Mulgedium floridanum (L.) DC.
  • Mulgedium villosum (Jacq.) Small
  • Sonchus floridanus L.

International Common Names

  • English: Florida blue lettuce; Florida lettuce; Florida wild lettuce; wild lettuce

Summary of Invasiveness

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L. floridana is a weedy lettuce which can grow to almost 2 metres tall (Randall, 2012), locally common in disturbed areas within its native range and only found outside North America in Puerto Rico, where it is considered invasive. It is a fast-growing, annual or biennial herb of gardens, roadsides, waste ground and pastures, and is native to moist and wet woodlands in North America. 

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Asterales
  •                         Family: Asteraceae
  •                             Genus: Lactuca
  •                                 Species: Lactuca floridana

Notes on Taxonomy and Nomenclature

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Asteraceae is one of the largest families of flowering plants with about 1620 genera and more than 23,600 species (Stevens, 2012). Vegetatively the members of this family are extremely variable, but they are readily recognized by their flowers (florets) in heads (capitula) surrounded by an involucre of bracts. The small, single-seeded fruit (cypsela) often have a plumose pappus, that aid in wind dispersal (Stevens, 2012).

The genus Lactuca has about 75 species and is mostly found in the temperate Northern Hemisphere and related to Cichorium and Sonchus. The genus name comes from the Latin word lac meaning milk, in obvious reference to the milky plant sap. Several of the species including L. serriola are cosmopolitan weeds, while L. sativa is widely grown for salads. L. floridana is currently only recognized as invasive in Puerto Rico. It is native to wet and moist woodlands and related to edible lettuce (L. sativa), hence the common names of wild or woodland lettuce.

Description

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Annual or biennial herbs 0.3–1.5(–2.2) m tall, with a long slender taproot. Stems solitary, erect; branches ascending, glabrous. Basal rosette leaves triangular-ovate to oblanceolate, 80-370 mm long, 2.5-180 mm wide, lyrate pinnatifid, hairs only on veins, on petioles 20-40 mm long; bases attenuate to clasping; margins dentate; lateral lobes 1 to 3 pairs, triangular; terminal lobes not distinctly larger than lateral ones; apices rounded to acute. Cauline leaves alternate, large diminishing and less divided toward stem apex; bases clasping; apices acute. Synflorescences paniculate, 0.4-0.8 m long. Capitula terminal on 10-20 mm peduncles, each with 10–27 florets. Involucres cylindric, 8–14 mm long, 4-5 mm diam.; outer phyllaries 5-8 lanceolate 2-7 mm long, erect; inner phyllaries 6-9 linear 6-10 mm long. Florets all ligulate, 5-7 mm long, linear, bluish-white. Cypselae brown, subcylindric to compressed 4-6 mm long, speckled rugulose with 4-6 ribs; beaks 0.1-1 mm long. Pappus numerous barbellate bristles 4-5 mm long, white (description compiled from Strother 2006; Weakley et al. 2012; Puttock pers. obs.).

Plant Type

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Biennial
Seed propagated

Distribution

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L. floridana has a native distribution covering much of the eastern United States and southeastern Canada (Manitoba and Ontario; Massachusetts south to Florida, west to Texas, and north to South Dakota and Minnesota). Although listed as native for Puerto Rico by USDA-ARS (2014), it is in fact introduced from North America (Acevedo-Rodriguez and Strong, 2012).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

North America

CanadaPresentPresent based on regional distribution.
-ManitobaPresentNativeUSDA-ARS, 2014SE Manitoba
-OntarioPresentNativeUSDA-ARS, 2014Southern Ontario
USAPresentPresent based on regional distribution.
-AlabamaWidespreadNative Not invasive USDA-ARS, 2014
-ArkansasWidespreadNative Not invasive USDA-ARS, 2014
-DelawareWidespreadNative Not invasive USDA-ARS, 2014
-District of ColumbiaWidespreadNative Not invasive USDA-ARS, 2014
-FloridaWidespreadNative Not invasive USDA-ARS, 2014
-GeorgiaWidespreadNative Not invasive USDA-ARS, 2014
-IllinoisWidespreadNative Not invasive USDA-ARS, 2014
-IndianaWidespreadNative Not invasive USDA-ARS, 2014
-IowaWidespreadNative Not invasive USDA-ARS, 2014
-KansasWidespreadNative Not invasive USDA-ARS, 2014
-KentuckyWidespreadNative Not invasive USDA-ARS, 2014
-LouisianaWidespreadNative Not invasive USDA-ARS, 2014
-MarylandWidespreadNative Not invasive USDA-ARS, 2014
-MassachusettsWidespreadNative Not invasive USDA-ARS, 2014
-MichiganWidespreadNative Not invasive USDA-ARS, 2014
-MississippiPresentNative Not invasive USDA-ARS, 2014
-MissouriWidespreadNative Not invasive USDA-ARS, 2014
-NebraskaWidespreadNative Not invasive USDA-ARS, 2014
-New JerseyWidespreadNative Not invasive USDA-ARS, 2014
-New YorkWidespreadNative Not invasive USDA-ARS, 2014
-OhioWidespreadNative Not invasive USDA-ARS, 2014
-OklahomaWidespreadNative Not invasive USDA-ARS, 2014
-PennsylvaniaWidespreadNative Not invasive USDA-ARS, 2014
-South CarolinaWidespreadNative Not invasive USDA-ARS, 2014
-South DakotaWidespreadNative Not invasive USDA-ARS, 2014
-TennesseeWidespreadNative Not invasive USDA-ARS, 2014
-TexasWidespreadNative Not invasive USDA-ARS, 2014
-VirginiaWidespreadNative Not invasive USDA-ARS, 2014
-West VirginiaWidespreadNative Not invasive USDA-ARS, 2014
-WisconsinWidespreadNative Not invasive USDA-ARS, 2014

Central America and Caribbean

Puerto RicoPresentIntroduced Invasive Acevedo-Rodriguez and Strong, 2012

History of Introduction and Spread

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L. floridana was first collected in Puerto Rico in 1885, in a Coffee Plantation (inter arbores “Caff. Arab.”) in the Central Mountains in 1885 (US National Herbarium). The species was first reported by Stahl (1887) and subsequently by Britton and Wilson (1923). Further collections suggest that the species is still restricted to the Central Mountain Range of the island (US National Herbarium). 

Risk of Introduction

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L. floridana has yet to spread to similar habitats worldwide. However, the risk of introduction to such ecosystems is high. This species has historically been dispersed by humans and has the potential to grow as a weed on roadsides, in ruderal areas, and in agricultural and pasture lands in the moist to dry subtropics.  

Habitat

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L. floridana grows in part to full shade, in moist to wet well drained floodplain forests, forest clearings and along stream banks, margins of ponds and lakes, savannah woodlands, and as a ruderal weed along railroads, roadsides, and open, disturbed areas. Found at 10-200 m.

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Terrestrial
Terrestrial – ManagedDisturbed areas Present, no further details
Rail / roadsides Present, no further details
Urban / peri-urban areas Present, no further details
Terrestrial ‑ Natural / Semi-naturalNatural forests Present, no further details
Natural grasslands Present, no further details
Riverbanks Present, no further details
Rocky areas / lava flows Present, no further details
Scrub / shrublands Present, no further details

Biology and Ecology

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Genetics

L. floridana is diploid with a chromosome number of 2n = 34 (Parfitt 1981; Love and Love 1982; Vahidy et al. 1987).  The base number (x) for Lactuca is 9 with a reduction to 8 in European and African species. Hybridization between these two series would give rise to the America taxa, all with n = 17. Such tests for crop improvement were attempted with little success by USDA (Thompson et al., 1941; Whitaker and Thompson, 1941; Thompson, 1943).

Reproductive Biology

Individual plants produce thousands of capitula, each with 10-27 florets. Florets in L. floridana are visited by bees (Pellett, 1915).

Longevity and Phenology

L. floridana is an annual or biennial herb germinating in spring and flowering in the southern part of its range from June through October. There is a shorter season in the northern part of its range, where it grows as an annual.          

Environmental Requirements

L. floridana needs partial shade and moderate water availability to grow. The plant favours loams of forest and river banks. A general slightly acidic to neutral soil pH is assumed based upon the forest cover (pH 6.5-7.0). 

Climate

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ClimateStatusDescriptionRemark
As - Tropical savanna climate with dry summer Preferred < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25])
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)
Df - Continental climate, wet all year Preferred Continental climate, wet all year (Warm average temp. > 10°C, coldest month < 0°C, wet all year)
Ds - Continental climate with dry summer Preferred Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)
Dw - Continental climate with dry winter Preferred Continental climate with dry winter (Warm average temp. > 10°C, coldest month < 0°C, dry winters)

Soil Tolerances

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Soil reaction

  • acid
  • neutral

Soil texture

  • medium

Means of Movement and Dispersal

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Once established in a new location L. floridana spreads locally by windborne seeds. Long distance dispersal can be attributed to humans. L. floridana can be anticipated as a contaminant in agricultural production: crop seeds, pasture seeds and in agricultural machinery.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Disturbance Yes Yes
Hitchhiker Yes Yes
People foraging Yes

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Clothing, footwear and possessions Yes Yes
Wind Yes

Plant Trade

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Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
Leaves

Impact Summary

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CategoryImpact
Environment (generally) Negative

Economic Impact

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L. floridana is a weed with little important economic impact.  

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Pioneering in disturbed areas
  • Tolerant of shade
  • Highly mobile locally
  • Benefits from human association (i.e. it is a human commensal)
  • Fast growing
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
  • Has high genetic variability
Impact outcomes
  • Damaged ecosystem services
  • Ecosystem change/ habitat alteration
  • Increases vulnerability to invasions
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
Impact mechanisms
  • Competition - shading
  • Rapid growth
  • Rooting
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Difficult to identify/detect as a commodity contaminant
  • Difficult/costly to control

Uses

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Leaves of L. floridana were used by American Indians as a potherb and as salad greens (Anon, 1922). 

Uses List

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Environmental

  • Wildlife habitat

General

  • Sociocultural value

Human food and beverage

  • Vegetable

Similarities to Other Species/Conditions

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The capitula of L. floridana are similar in appearance to those of Cichorium intybus (chicory), but the heads of that species form in the leaf axils, not terminal on a panicle.

Prior to flowering, this species is very similar to L. canadensis, but can be distinguished by the colour of the sap. The sap of L. canadensis is light- salmon pink in colour, whereas that of L. floridana is milky white.

References

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Acevedo-Rodríguez P; Strong MT, 2012. Catalogue of the Seed Plants of the West Indies. Smithsonian Contributions to Botany, 98:1192 pp. Washington DC, USA: Smithsonian Institution. http://botany.si.edu/Antilles/WestIndies/catalog.htm

Anon, 1922. Plants of our local flora which have been used by man as food. Missouri Botanical Garden Bulletin, 10:102-110.

Britton NL; Wilson P, 1923. Scientific Survey of Porto Rico and the Virgin Islands Vol. 5, Part 1. New York, USA: New York Academy of Sciences, 626 pp.

Love A, 1982. IOPB chromosome number reports LXXV. Taxon, 31(2):342-368.

Parfitt BD, 1981. Chromosome number reports LXXI. Taxon, 30:515-516.

Pellett F, 1915. No.11. The honey-producing plants. American Bee Journal, 55:379-380.

Randall RP, 2012. A Global Compendium of Weeds. Perth, Australia: Department of Agriculture and Food Western Australia, 1124 pp. http://www.cabi.org/isc/FullTextPDF/2013/20133109119.pdf

Stahl A, 1887. Estudios para la flora de Puerto Rico. Folletos 2-6 ([English title not available]).

Stevens PF, 2012. Angiosperm Phylogeny Website. http://www.mobot.org/MOBOT/research/APweb/

Strother JL, 2006. Lactuca. In: Flora of North America North of Mexico, 21 [ed. by Flora of North America Editorial Committee]. New York and Oxford, USA and UK: Flora of North America Editorial Committee.

THOMPSON RC, 1943. Further studies on interspecific genetic relationships in Lactuca. Journal of Agricultural Research, 66:41-18.

THOMPSON RC; WHITAKER TW; KOSAR WF, 1941. Interspecific genetic relationships in Lactuca. Journal of Agricultural Research, 63:91-107.

USDA-ARS, 2014. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx

Vahidy AA; Davidse G; Shigenobu Y, 1987. Chromosome counts of Missouri Asteraceae and Poaceae. Annals of the Missouri Botanical Garden, 74(2):432-433.

Weakley AS; Ludwig JC; Townsend JF, 2012. Flora of Virginia., USA: Botanical Research Institute of Texas, 1572 pp.

Whittaker TW; Thompson RC, 1941. Cytological studies in Lactuca. Torrey Botanical Club Bulletin, 68:388-394.

Links to Websites

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WebsiteURLComment
Catalogue of Seed Plants of the West Indieshttp://botany.si.edu/antilles/WestIndies/catalog.htm
Global Compositae Checklisthttp://compositae.landcareresearch.co.nz/Default.aspx

Contributors

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03/10/2014 Original text by:

Christopher F. Puttock, Department of Botany-Smithsonian NMNH, Washington DC, USA

Pedro Acevedo-Rodríguez, Department of Botany-Smithsonian NMNH, Washington DC, USA

Distribution Maps

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