Lactuca canadensis L. - Tall Lettuce


 

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Lactuca canadensis - (image 1 of 4)

 

Taxonomy

Family: Asteraceae

Habitat

Fields, waste places, woods.

Associates

 

Distribution

Quebec and Prince Edward Island to Saskatchewan, south to FL and TX.

Morphology

Herbaceous biennial, sometimes annual; stems 0.3-2.5 m, glabrous or coarsely hirsute, often more or less glaucous; leaves variable, entire or toothed to pinnately lobed or cleft, sagittate or sometimes narrowed to the base, to 35 cm long; heads numerous, small, with 13-22 yellow flowers; involucres 10-15 mm in fruit; achenes blackish, very flat, with a median nerve on each face, transversely rugulose, 4.5-6.5 mm total length, the slender beak from a little more than half to about as long as the body; mature pappus 5-7 mm.

Notes

Flowers July to September

Wetland indicator: FACU

Differs from other species with small flower heads (involucres 10-15 mm in fruit) in having a single median nerve on each face of the achene.

  References

Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. Second Ed.
The New York Botanical Garden. Bronx, NY.

 


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 Michael Hough © 2018