woolly burdock

(Arctium tomentosum)

Conservation Status
woolly burdock
  IUCN Red List

not listed

     
  NatureServe

NNA - Not applicable

     
  Minnesota

not listed

     
           
           
           
 
Description
 
 

Woolly burdock is a 2 to 4 tall, rarely taller, erect, biennial forb that rises on a single stem from a fleshy taproot. In its first year of growth this produces a rosette of basal leaves. In the second year it produces a hollow stalk that is branched, hairy, and ridged.

Basal leaves are large, heart shaped and indented at the base where they attach to the leaf stalks. They are 12 to 15 long and 6 to 11 wide. The leaf stalk is 4 to 6 long, mostly hollow, and is covered with glandular hairs. The upper surface of the blade is green with sparse short hairs. The lower surface is light green or gray-green, with a thin covering of white, matted, short, soft, woolly hairs. The margins are wavy and are untoothed or may have small teeth. By the time the flowers are fully open the basal leaves are usually withered.

Stem leaves are much smaller, alternate, and egg-shaped, getting progressively smaller toward the top of the stem.

The inflorescence is a cluster of stalked flower heads with the outer ones on longer stalks, forming a flat-topped or convex cluster. The clusters appear at the end of the stem and in the upper leaf axils.

Flower heads have about 30 rose purple, occasionally white, florets, are ½ to 1 wide, and are on ½ to 4¾ long stalks. The whorl of overlapping bracts subtending the flower head is 1 to 1½ in diameter and is densely woolly or cobwebby. The bracts are hooked at the tip. When dry the flower head becomes a bur resembling a thistle. Thistles, however, do not have hooked bracts.

 
     
 

Height

 
 

2 to 4, rarely taller

 
     
 

Flower Color

 
 

Rose purple, occasionally white

 
     
 

Similar Species

 
 

Common burdock (Arctium minus) leaves are usually more wavy. The flower heads are not densely cobwebby and are on short stalks or no stalks at all.

Great burdock (Arctium lappa) has flower heads on long stalks. The inflorescence is a group of stalked flower heads with the outer ones on longer stalks, forming a flat-topped or convex cluster.

 
     
 
Habitat
 
 

Disturbed sites, roadsides.

 
     
 
Biology
 
 

Flowering

 
 

July to October

 
     
 
Use
 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

2, 3, 4, 5, 7, 22, 29, 30.

The Bell Herbarium has only two records of this plant. Both were before 1960 on or near the Red River in St. Vincent.

 
  3/15/2021      
         
 

Nativity

 
 

Native to Asia and Europe. Introduced and naturalized in the United States. Potentially invasive.

 
         
 

Occurrence

 
 

Uncommon. Locally common in southwestern Minnesota.

 
         
 
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 Carduoideae (thistles and allies)  
  Tribe Cynareae (= Cardueae)  
  Subtribe Carduinae (thistles and burdocks)  
  Genus Arctium (burdock)  
       
 

Cardueae is a synonym of the tribe name. Cynareae was published first and has precedence. Nevertheless, most sources use the name Cardueae for the tribe.

 
       
 

Subordinate Taxa

 
 

 

 
       
 

Synonyms

 
 

Arctium leptophyllum

Lappa tomentosa

 
       
 

Common Names

 
 

cotton burdock

hairy burdock

woolly burdock

 
       

 

 

 

 

 

Glossary

Axil

The upper angle where the leaf stalk meets the stem.

 

Glandular hairs

Hairs spread over aerial vegetation that secrete essential oils. The oils act to protect against herbivores and pathogens or, when on a flower part, attract pollinators. The hairs have a sticky or oily feel.

       
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Habitat

  woolly burdock    
       

Plant

  woolly burdock   woolly burdock
       

Inflorescence

  woolly burdock   woolly burdock
       
  woolly burdock    
       

Flower Heads

  woolly burdock   woolly burdock
       

Leaf Upper Side

  woolly burdock    
       

Leaf Underside

  woolly burdock    
       

Stem

  woolly burdock    
       
       

 

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Other Videos
 
  Schamloses Treiben von Harmonia axyridis auf Arctium tomentosum (1)
URSchmidt
 
   
 
About

Published on Jul 1, 2012

Pärchen von Harmonia axyridis bei der Begattung

   
       

 

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