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
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:
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|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.|
|Habitats||Redwood forest, wetlands||Woodland margins, clearings, near the edges of water, roadsides, pastures.||Grasslands, seasonal wetlands, orchards, vineyards, urban places, roadsides, disturbed habitats.|
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 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 CalPhotos
Lactuca biennis on eFloras
Thierer, John W., Niering, William A, Olmstead, Nancy C., National Audabon Society Field Guide to North American Wildflowers, Eastern Region, Alfred A. Knopf, 2001, p. 405
Lactuca biennis description by Thomas H. Kent, last updated 25 May 2020.