Lactuca biennis (Moench) Fern.
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TAXONOMY
 
Family: Asteraceae or Compositae
Genus: Lactuca
 
Species Synonyms: Mulgedium spicatum auct. non (Lam.) Small
Mulgedium spicatum var. integrifolium (Torr. & Gray) Small
Lactuca spicata var. integrifolia (Torr. & Gray) Britt.
Lactuca spicata auct. Non (Lama.) A.S. Hitchc.
Common Names: tall blue lettuce
wild blue lettuce
blue wood lettuce
 
DISTRIBUTION
 
Canada: southern Yukon Territory – British Columbia – Labrador –Newfoundland – Nova Scotia
Saskatchewan: southern and central Saskatchewan
Ecoregion: Cypress Upland, Aspen Parkland, Boreal Transition, Mid-Boreal Upland, Mid-Boreal Lowland, Churchill River Upland
 
HABITAT
 
Saskatchewan: moist woods and shrub thickets
Associated Species: Alnus incana, Cicuta maculata, Thalictrum venulosum, Vicia americana, Viburnum edule
 
RARITY STATUS
 
Provincial Status According
to Harms (2003):
Vulnerable
Nature Conservancy Status:
G5 S2
Saskatchewan Species at
Risk Status:
None
COSEWIC Status:
None
 
Lactuca biennis is apparently quite secure, with numerous populations throughout the province. However, local populations are small, leaving this plant vulnerable to changes in habitat.
 
SPECIES DESCRIPTION
 
Height: 1 – 2.5 m tall
Roots: taproot
Stems: to 1.5 cm wide, glabrous
Leaves: basal and lower leaves sessile, base attenuate to sagittate, apex broadly deltate, trichomes present, margin dentate; middle and upper leaves with decurrent petiole, 10 – 25 cm long, 5 – 10 cm wide, base attenuate to sagittate, pubescent on midvein, glabrous above, pinnately lobed to entire, sometimes runcinate; upper leaves narrow, auriculate clasping, margin entire
Inflorescence: heads 50 – 100 in conical panicle, ligulate florets only; phyllaries ~24 in several imbricate series, black-tipped
Flowers: ligulate florets 25 – 40, blue or creamy white
Fruits: achenes 3 – 5 mm long, several nerved, flattened, grey to reddish brown; beak brown, stout, to 1 mm long, or absent; pappus of capillary bristles in 3 or 4 series, short outer pappus, tawny to greyish
 
KEY TO LACTUCA IN SASKATCHEWAN
 
1 Pappus brown or grey
L. biennis
1 Pappus white
2
   
2 Flowers yellow (may dry purple)
3
2 Flowers purple (may have some yellow)
4
   
3 Leaves prickly on margin; heads with 6 – 12 florets; latex white
L. serriola
3 Leaves not prickly on margin; heads with 12 – 20 florets; latex brown
L. ludoviciana
 
4 Leaves prickly on margin; latex white (flowers only purplish when dried)
L. serriola
4 Leaves not prickly on margin; latex white or brown
5
 
5 Plants not glaucous; achenes very flat, median nerve strong, other nerves if present, obscure, beak long and slender; latex brown
L. ludoviciana
5 Plants glaucous; achenes moderately compressed, several prominent nerves, beak short; latex white
L. tartarica var. pulchella