tall blue lettuce

(Lactuca biennis)

               
Conservation Status

IUCN Red List

not yet assessed

tall blue lettuce

NatureServe

NNR - Unranked

SNR - Unranked

Minnesota

not listed

Wetland
Indicator
Status

Great Plains

FAC - Facultative

Midwest

FAC - Facultative

Northcentral & Northeast

FAC - Facultative

Nativity

Native

Occurrence

 

Habitat

Moist. Thickets, stream banks, woods.

Flowering

July to September

     
Flower Color

Bluish to white

     
Height

2 to 6½

     

Identification

This is a 2 to 6½ tall, erect, annual or biennial forb with a thick, deep taproot. The stems and leaves contain a milky latex.

The stems are leafy and hairless.

The alternate leaves are lobed halfway or more to the midrib but not reaching the midrib. They are up to 4 to 16 long and 1½ to 8 wide. They are attached to the stem without a leaf stalk, with the base partly surrounding the stem (clasping). The main veins on the underside are hairy.

The inflorescence is a terminal tall, narrow, crowded cluster, and small clusters in the leaf axils.

The flower heads are about across and have 15 to 50, usually 20 to 30, bluish to white ray florets.

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

 
Similar
Species

Canada lettuce (Lactuca canadensis) has yellow flowers.

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.

Showy blue lettuce (Lactuca tatarica ssp. pulchella) has large, showy flower heads that measure, ¾ across. The achene has white bristles attached to the tip.

Woodland lettuce (Lactuca floridana var. floridana) has a more open inflorescence and tends to be less leafy than tall blue lettuce. The flower heads have 10 to 15 ray florets. The achene has white bristles attached to the tip.


Distribution Distribution Map   Sources: 2, 3, 4, 5, 7, 28.

Comments

 


Taxonomy

Family:

Asteraceae (aster)

 

Subfamily:

Cichorioideae

 

Tribe:

Cichorieae

 

Subtribe:

Lactucinae

 
Synonyms

Lactuca spicata

Lactuca spicata var. integrifolia

Mulgedium spicatum

Mulgedium spicatum var. integrifolium

Sonchus biennis

 
Common
Names

biennial blue lettuce

biennial lettuce

tall blue lettuce

wild blue lettuce

wild lettuce

woodland lettuce


 

 

 

 

 

 

 

 

 

Glossary

achene

A dry, one-chambered, single-seeded fruit, formed from a single carpel, with the seed attached to the membranous outer layer (wall) only by the seed stalk; the wall, formed entirely from the wall of the superior ovary, does not split open at maturity, but relies on decay or predation to release the contents.

 

clasping

Describing a leaf that wholly or partly surrounds the stem but does not fuse at the base.

       

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