Wild Lettuce

Plants of the Eloise Butler Wildflower Garden
The oldest public wildflower garden in the United States






Wild Lettuce
Lactuca canadensis L.
Aster (Asteraceae)
Woodland and Upland
Late Summer to early Autumn
Other names and notes

(Canada Lettuce, Tall Lettuce). Wild Lettuce grows as a tall, erect annual or biennial, reaching up to 8 feet high. Stems are leafy, smooth, light green or reddish green, sometimes have purple streaks, and contain a milky juice and are unbranched until the inflorescence. Leaves vary considerably, from entire to toothed, to pinnately divided and have a narrow unstalked base or a clasping base. Larger leaves tend to have deep pinnate lobes, smaller upper leaves maybe entire with a sessile base. The leaf edges are not spiny, teeth are widely spaced and the underside of the midrib vein will have fine short hair. Inflorescence: Flowers appear in a loosely branched panicle that is long and cone shaped and contains many flower heads. It is late flowering and the inflorescence will have buds, flowers and seed heads at the same time. The flowers, resembling dandelions, are small ( under 3/8 inch) with 15 to 20+ yellowish ray flowers (some plants have bluish corollas), flower heads are longer than wide. The phyllaries of the flower head are in several series with the outer ones shorter than the linear inner ones. These reflex when the head is in fruit. Each flower rapidly absorbs moisture and fades away the same day it opens - said to be 'deliquescent'. Seeds are a oblong-oval dry achene, with one noticeable nerve line on the side (although they may be up to 3 on some) and are transported by the wind via a tuft of white hair (pappus).

Habitat: Wild Lettuce grows from a deep taproot. It tolerates poorer soils but does best in fertile loam and full sun, while some shade is tolerated as are moist to dry conditions. Names: The genus Lactuca is applied to the lettuce family and comes from the Latin lac, for the milky juice of the stem and root. The species canadensis means 'of Canada', the original type location. The author name for the plant classification - 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. Comparisons: A similar plant is Prickly Lettuce, Lactuca serriola, but there the leaves have prickly edges and spines on the underside of the midrib. Blooming earlier, but still around at the time Wild Lettuce blooms are the Sow Thistles. The flowers of of Spiny Sow Thistle, Sonchus asper, somewhat resemble Wild Lettuce but are slightly wider and the leaves also are prickly. The most similar plant is Tall Blue Lettuce, L. biennis, but there the florets are mostly bluish or cream-colored and the leaves a darker shade.

Wild Lettuce Seedhead
Above: A flower with 17 rays. Flower are only open part of a day. Below: The basal rosette of next years plant.
Above: The seed head of Wild Lettuce. Note the reflexed phyllaries. Below: Detail of the individual seeds (achenes) with their fluffy white hair attached to a long beak.
Wild Lettuce base rosette
Wild Lettuce Seed
Below: An example of the larger leaves, deeply lobed with a narrow sessile base and few, widely spaced teeth. Far Below: an upper stem leaf.
Below: Detail of the flower buds. The outer phyllaries are shorter than the inner. Far below: The main greenish-red stem.
Below: The inflorescence with flowering mostly over and some seed heads with the fluffy white pappus ready to take to the air. Far below: Prior to flower opening.
Wild Lettuce Leaf
Wild Lettuce inflorescence
Wild Lettuce upper leaf Wild Lettuce

Notes: Wild Lettuce is indigenous to the Garden area. It is found in North America in all the Canadian Provinces except the far north and Saskatchewan and in all the lower 48 states except Arizona and Nevada. In Minnesota it is known in all counties in the NE quadrant, most of the SE and NW quadrants, with most exceptions being in the dryer SW quadrant. There are five species of Wild Lettuce in Minnesota including L. canadensis. The other four are: (Tall) Biennial Blue Lettuce, L. biennis; Florida Wild Lettuce, L. floridana; and Louisiana Lettuce, L. ludoviciana - all those being native - and finally the introduced Prickly Lettuce, L. serriola.

Lore: Densmore (Ref.#5) reports that a use of this plant for warts was common amount the Minnesota Chippewa. She was told "Gather the white liquid which comes out when the stalk is broken and rub this on the wart."


References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applies. Distribution principally from Wi, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.  
©2013 Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org" 012215