blue lettuce

not listed

N4N5 - Apparently Secure to Secure

SNR - Unranked

not listed

UPL - Obligate upland

FAC - Facultative

FAC - Facultative

Blue lettuce is a 1′ to 4′ tall, erect, perennial forb rising on usually a single stem from deep-seated, creeping roots. The stems and leaves contain a milky latex.

The stems are leafy and hairless.

The leaves are bluish-green, alternate, and unlobed or with narrow lobes. The underside of the leaves are often covered with a white, waxy bloom.

The inflorescence is several heads in a branched cluster.

The flower heads are about ¾″ across and have 10 to 50, usually at least 15, ray florets.

The fruit is a reddish-brown achene with fluffy, white bristles attached to the tip.

1′ to 4′

Blue to purple

This plant is easily distinguished from other lettuce species by its large, showy flowers.

Canada lettuce (Lactuca canadensis) has yellow flowers.

Prairie lettuce (Lactuca ludoviciana) has prickles along the leaf margins and on the midvein on the underside of the leaf.

Prickly lettuce (Lactuca serriola) has yellow flowers. The leaves have prickles on the leaf margins and on the underside of the midvein.

The blue species of Lactuca are extremely variable and identifying characteristics overlap, factors which, taken together, make the species difficult to separate.

Tall blue lettuce (Lactuca biennis) has smaller flower heads that are about ⅜″ across. The achene has grayish-brown bristles attached to the tip.

Woodland lettuce (Lactuca floridana var. floridana) has smaller flower heads that are about ⅜″ across.

Moist. Meadows, thickets, prairies.

June to September

Sources

2, 3, 4, 5, 7, 28, 29, 30.

Native

Considerable disagreement continues about the proper scientific name for this plant. Six names are currently (3/16/2023) in use by widely respected authorities.

ITIS classifies it as Mulgedium oblongifolium;

The Plant List, FNA, NCBI, Minnesota DNR (MNTaxa), and Minnesota Biodiversity Atlas (Bell Herbarium) as Mulgedium pulchellum;

The Global Compositae Database, BONAP, and iNaturalist as Lactuca tatarica;

GRIN and Steyermark’s Flora of Missouri (Yatskievievyck, 2006) as Lactuca tatarica ssp. pulchella;

USDA PLANTS as Lactuca tatarica var. pulchella;

Plants of the World Online, World Flora Online, GBIF, iNaturalist, NatureServe, Manual of Vascular Plants (Gleason and Cronquist, 1992), and Flora of Minnesota (Chadde, Second Edition, 2019) as Lactuca pulchella.