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Lactuca biennis

Lactuca biennis (Moench) Fernald

Lactuca spicata auct. non (Lam.) Hitchc.

Lactuca spicata (Lam.) Hitchc. var. integrifolia (Torr. & A. Gray) Britton

Mulgedium spicatum auct. non (Lam.) Small

Mulgedium spicatum (Lam.) Small var. integrifolium (Torr. & A. Gray) Small

Tall Blue Lettuce

KingdomPlantaePlants, but not fungi, lichens, or algae (from Stearn’s Botanical Latin)
SubkingdomTracheobiontaVascular plants—plants with a “circulatory system” for delivering water and nutrients
DivisionMagnoliophytaFlowering plants, also known as angiosperms
ClassMagnoliopsidaDicotyledons—plants with two initial seed leaves
SubclassAsteridaeA large class that encompasses asters
OrderAsteralesFlowering plants with a central disk flower and surrounding petals, like daisies
FamilyAsteraceaeThe aster family, which also includes daisies and sunflowers; from the Greek ἀστήρ, “star,” for the star-shaped flowers
GenusLactucaFrom lacta, Latin for “milk,” referring to the milky sap in stem, and a root word for lactic acid
SpeciesbiennisBiennial, completing the life cycle in two growing seasons, usually blooming and fruiting in the second

About plant names...

This wild lettuce is native to eastern North America, and has been introduced to much of the rest of the continent as well. It is called tall blue lettuce because its flowers are blue.

Some Lactuca species:

 

Lactuca biennis (Tall Blue Lettuce)

9/5/2010 · Nashua River Rail Trail, near Nashoba Hospital, Ayer, MA
≈ 10 × 15" (26 × 39 cm) ID is uncertain

Lactuca biennis (Tall Blue Lettuce)

6/3/2016 · Nashua River Rail Trail, East Pepperell

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Lactuca biennis

Lactuca canadensis

Lactuca serriola
Common Name

Tall Blue Lettuce

Wild Lettuce

Prickly Lettuce
Plant Tall blue lettuce grows up to 6' (1.8 m) high. 4-10' (1.2-3 m) tall, with stems that are green or spotted with purple. The latex from a broken stem is brown. Erect, 12-79" (30-200 cm) tall. Stems sometimes have stiff hairs near the bottom; stems and leaves have a milky sap when cut.
Flowers Blue, about ¼-½" (6.3-12 mm) across, in crowded clusters at the top. At the top, large cone-shaped panicles consisting of 50-100 flowers appear. Individual flowers are about ¼" (8.5 mm) around, with 15-22 florets (tiny petals) each. They are yellow, pinkish-orange, or reddish. In panicles that form open, roughly conical clusters of flowers. Flowers are ⅜-½" (1-1.5 cm) in diameter, and have 13-27 florets (petals) each. Flowers appear July-September.
Leaves Leaves are deeply divided, like those of dandelions, but while dandelion leaves are roughly the same width along their length, these are more triangular in overall shape. They are up to 12" (30 cm) long and 6" (15 cm) wide at the base, tapering to sharp tips. Leaves are hairy, undersides more so. Vary greatly in shape, and may resemble the shape of a sickle, or long and narrow, or wider and deep lobes. They are 6-14" (15-35 cm) long. Alternate, 1¾-12" (5-30 cm) long and ⅜-4" (1-10 cm) wide. The mid-ribs of leaves have prickers along the bottom. Typically leaves are deeply lobed.
Fruit   Achenes (seeds) are small and brown, each with a “parachute” attached, like dandelions. ⅛" (3 mm) long, single-seeded, lance-shaped, attached to a “parachute” like dandelions.
Range/ Zones

Habitats Redwood forest, wetlands Woodland margins, clearings, near the edges of water, roadsides, pastures. Grasslands, seasonal wetlands, orchards, vineyards, urban places, roadsides, disturbed habitats.
Type Wild Wild Wild
Occurrence Common Common Common

 

Identification: Tall blue lettuce grows up to 6' (1.8 m) high. Its leaves are deeply divided, like those of dandelions, but while dandelion leaves are roughly the same width along their length, these are more triangular in overall shape. They are up to 12" (30 cm) long and 6" (15 cm) wide at the base, tapering to sharp tips. Leaves are hairy, undersides more so. Flowers are blue, about ¼-½" (6.3-12 mm) across, in crowded clusters at the top.

There are two similar species of wild lettuce with blue flowerheads. Lactuca floridana, florida lettuce or false lettuce, reaches 9' (2.7 m) in height, and has loose clusters of blue, sometimes whitish flowers. L. pulchella, large-flowered blue lettuce, has fewer, larger flowers, and its foliage is covered with a waxy, whitish bloom. The blue flowers look similar in shape and color to those of wild chicory, but the foliage is very different.

Lactuca biennis (Tall Blue Lettuce)

From Britton, Nathaniel Lord, and Brown, Addison, An illustrated flora of the northern United States, Canada and the British Possessions, 1913.

Online References:

Lactuca biennis at Minnesota Wildflowers

Lactuca biennis on Delaware Wildflowers

Lactuca biennis on Plants for a Future, a resource and information centre for edible and otherwise useful plants

Lactuca biennis at the University of Wisconsin's Robert W. Freckmann Herbarium

Lactuca biennis at the Lady Bird Johnson Wildflower Center

Lactuca biennis on the University of Massachusetts Landscape, Nursery & Urban Forestry Program

Lactuca biennis on Keir Morse's site, Keirosity.com

Lactuca biennis on CalPhotos

Lactuca biennis on eFloras

References:

Thierer, John W., Niering, William A, Olmstead, Nancy C., National Audabon Society Field Guide to North American Flowers, Eastern Region, Alfred A. Knopf, 2001, p. 405

Lactuca biennis (Tall Blue Lettuce)

8/18/2010 · J. Harry Rich Woods, off Nod Rd., Groton, MA
≈ 3½ × 5" (9.2 × 13 cm)

Lactuca biennis (Tall Blue Lettuce)

8/4/2009 · Near Nashoba Hospital, Ayer, MA
≈ 3½ × 5½' (1.1 × 1.7 m) ID is uncertain

Lactuca biennis (Tall Blue Lettuce)

6/3/2016 · Nashua River Rail Trail, East Pepperell

Lactuca biennis (Tall Blue Lettuce)

8/2/2012 · Nashua River Rail Trail, near Nashoba Hospital, Ayer, MA

Lactuca biennis (Tall Blue Lettuce)

8/18/2010 · J. Harry Rich Woods, off Nod Rd., Groton, MA
≈ 7 × 4½" (17 × 11 cm)

Lactuca biennis description by Thomas H. Kent, last updated 5 Oct 2016.

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Lactuca biennis (Tall Blue Lettuce)

8/14/2015 · Roost Trail, Grafton Notch State Park, Newry, Maine
≈ 4½ × 7" (11 × 16 cm)

Lactuca biennis (Tall Blue Lettuce)

8/18/2010 · J. Harry Rich Woods, off Nod Rd., Groton, MA
≈ 3 × 4½" (7.9 × 11 cm)

Lactuca biennis (Tall Blue Lettuce)

8/14/2015 · Roost Trail, Grafton Notch State Park, Newry, Maine
≈ 7 × 10" (16 × 25 cm)

Lactuca biennis (Tall Blue Lettuce)

7/27/2009 · Nashua River Rail Trail, Groton, MA
≈ 26 × 39" (65 × 98 cm) ID is uncertain

Lactuca biennis (Tall Blue Lettuce)

8/2/2012 · Nashua River Rail Trail, near Nashoba Hospital, Ayer, MA

Lactuca biennis (Tall Blue Lettuce)

8/18/2010 · J. Harry Rich Woods, off Nod Rd., Groton, MA
≈ 5 × 8" (13 × 19 cm)

Lactuca biennis (Tall Blue Lettuce)

6/11/2014 · Conservation Area near Potanipo Pond, Brookline, NH
≈ 12 × 8" (31 × 21 cm)

Lactuca biennis (Tall Blue Lettuce)

6/11/2014 · Conservation Area near Potanipo Pond, Brookline, NH
≈ 15 × 10" (37 × 25 cm)

Range:

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