tall blue lettuce

(Lactuca biennis)

Conservation Status
tall blue lettuce
  IUCN Red List

not listed

     
  NatureServe

NNR - Unranked

SNR - Unranked

     
  Minnesota

not listed

     
           
Wetland Indicator Status
     
  Great Plains

FAC - Facultative

     
  Midwest

FAC - Facultative

     
  Northcentral & Northeast

FAC - Facultative

     
           
 
Description
 
 

Tall blue lettuce 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.

 
     
 

Height

 
 

2 to 6½

 
     
 

Flower Color

 
 

Bluish to white

 
     
 

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.

 
     
 
Habitat
 
 

Moist. Thickets, stream banks, woods.

 
     
 
Biology
 
 

Flowering

 
 

July to September

 
     
 
Use
 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

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

 
  10/14/2015      
         
 

Nativity

 
 

Native

 
         
 

Occurrence

 
 

 

 
         
 
Taxonomy
 
  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (flowering plants)  
  Superorder Asteranae  
 

Order

Asterales (sunflowers, bellflowers, fanflowers, and allies)  
 

Family

Asteraceae (sunflowers, daisies, asters, and allies)  
  Subfamily Cichorioideae (chicories, dandelions, and allies)  
  Tribe Cichorieae  
  Subtribe Lactucinae  
  Genus Lactuca (lettuce)  
       
 

Subordinate Taxa

 
 

 

 
       
 

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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Plant

  tall blue lettuce    
       

Inflorescence

  tall blue lettuce   tall blue lettuce
       

Flower Heads

  tall blue lettuce    
       

Leaves

  tall blue lettuce   tall blue lettuce
       
  tall blue lettuce    
       

Stem

  tall blue lettuce    
       
       

 

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