Lactuca biennis (Tall blue lettuce)

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Lactuca biennis (Moench) Fernald

Tall blue lettuce

Kingdom	Plantae	Plants, but not fungi, lichens, or algae
Subkingdom	Tracheobionta	Vascular plants—plants with a “circulatory system” for delivering water and nutrients
Division	Magnoliophyta	Flowering plants, also known as angiosperms
Class	Magnoliopsida	Dicotyledons—plants with two initial seed leaves
Subclass	Asteridae	A large class that encompasses asters
Order	Asterales	Flowering plants with a central disk flower and surrounding petals, like daisies
Family	Asteraceae	The aster family, which also includes daisies and sunflowers; from the Greek ἀστήρ, “star,” for the star-shaped flowers
Genus	Lactuca	From lacta, Latin for “milk,” referring to the milky sap in stem, and a root word for lactic acid
Species	biennis	Biennial, 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:

9/5/2010 · Nashua River Rail Trail, near Nashoba Hospital, Ayer, Massachusetts
≈ 10 × 14" (26 × 35 cm) ID is uncertain

7/17/2013 · Near Nashua River Boat Ramp, Groton, Massachusetts

	You are here 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.

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

Online References:

Minnesota Wildflowers

Delaware Wildflowers

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

The University of Wisconsin's Robert W. Freckmann Herbarium

The Lady Bird Johnson Wildflower Center

The University of Massachusetts Landscape, Nursery & Urban Forestry Program

CalPhotos

EFloras

References:

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

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

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

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

9/1/2018 · Bates Land and Blackman Land, Groton Conservation Trust, Groton, Massachusetts
≈ 6 × 10" (16 × 24 cm)

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

9/1/2018 · Bates Land and Blackman Land, Groton Conservation Trust, Groton, Massachusetts
≈ 10 × 15" (26 × 39 cm)

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

Lactuca biennis description by Thomas H. Kent, last updated 16 Sep 2020.

6/5/2012 · Nashua River Rail Trail, Groton Center, Groton, Massachusetts
≈ 14 × 21" (34 × 52 cm)

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

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

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

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

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

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

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

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

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

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

Range:

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