prairie ironweed

(Vernonia fasciculata ssp. fasciculata)

Conservation Status
prairie ironweed (ssp. fasciculata)
  IUCN Red List

not listed

     
  NatureServe

NNR - Unranked

SNR - Unranked

     
  Minnesota

not listed

     
           
Wetland Indicator Status
     
  Great Plains

FAC - Facultative

     
  Midwest

FACW - Facultative wetland

     
  Northcentral & Northeast

FACW - Facultative wetland

     
           
 
Description
 
 

Prairie ironweed (ssp. fasciculata) is a 20 to 55 tall, erect, perennial forb that rises on a single stem or a clump of 2 or more stems from a stout, thickened rootstock.

The stems are erect, round, light green or reddish-purple, and unbranched below the inflorescence. The are usually hairless but are sometimes minutely hairy near the top.

The leaves are alternate, stalkless or on short leaf stalks, narrowly to broadly lance-shaped, 2 to 7 long, and to 1½ wide. The leaf blades are tapered at the base and taper to a sharp point at the tip. The upper surface is green, smooth to the touch, and mostly hairless but may have fine short hairs near the margin. The lower surface is similar in color, hairless, and dotted with minute pitted glands. The glands appear as translucent dots when the leaf is held up to the sun or another light source. The margins are sharply toothed.

The inflorescence is a dense, branched, 1½ to 4 wide, flat-topped cluster (cyme) of many flower heads at the end of the stem. The flower heads within the cyme are not grouped into secondary head-like clusters.

The base of each flower head (involucre) is bell shaped, 3 16 to long and to ¼ high. The involucre is composed of 25 to 35 or more modified leaves (bracts) in 4 or 5 overlapping series. The involucral bracts (phyllaries) are to ¼ long, and their tips are pressed closely to the involucre. They are green but usually tinged purplish along the midvein and toward the tip. They are mostly hairless on the back but sometimes have sparse, long, cobwebby hairs on the margins. The outer phyllaries are broad and scale-like. The inner ones are narrow.

Each flower head has 10 to 26 disk florets and no ray florets. The disk florets are purple and to 7 16 long. They are tube-shaped at the base then separated into 5 long, widely spreading lobes. The flowers have no noticeable scent.

The fruit is a dry, brown, one-seeded, 1 16 to long seed capsule (cypsela) with a modified calyx (pappus) is attached to one end. The pappus is in two series: an outer ring of 20 to 30 minute scales, and an inner tuft of 35 to 45 tan to brownish-purple, 3 16 to ¼ long hair-like bristles.

 
     
 

Height

 
 

20 to 55

 
     
 

Flower Color

 
 

Reddish purple

 
     
 

Similar Species

 
 

Western ironweed (Vernonia fasciculata ssp. corymbosa) is a much shorter plant, reaching only 12 to 24 in height at maturity. The leaves on the main part of the stem are shorter, 1½ to 4 long, wider, and rough to the touch on the upper surface near the margins. In Minnesota it is found only in the western border counties and in the southwest.

Baldwin’s ironweed (Vernonia baldwinii ssp. interior) has hairs on the underside of the leaves that obscure any translucent dots. The tips of the bracts in the involucre curve backward. It has been reported only in Crow Wing (in1890) and Goodhue (in 2000) Counties.

 
     
 
Habitat
 
 

Wet to moderate moisture. Prairies, meadows, pastures, marshes. Full sun.

 
     
 
Biology
 
 

Flowering

 
 

July to September

 
     
 
Use
 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

7.

 
  1/9/2020      
         
 

Nativity

 
 

Native

 
         
 

Occurrence

 
 

Common

 
         
 
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 (dicots)  
  Superorder Asteranae  
 

Order

Asterales (sunflowers, bellflowers, fanflowers, and allies)  
 

Family

Asteraceae (sunflowers, daisies, asters, and allies)  
  Subfamily Cichorioideae (chicories, dandelions, and allies)  
  Tribe Vernonieae (ironweed)  
  Subtribe Vernoniinae  
  Genus Vernonia (ironweed)  
  Species Vernonia fasciculata (prairie ironweed)  
       
 

Subordinate Taxa

 
 

 

 
       
 

Synonyms

 
 

 

 
       
 

Common Names

 
 

bunched ironweed

common ironweed

ironweed

prairie ironweed

smooth ironweed

 
       

 

 

 

 

 

 

 

 

Glossary

Bract

Modified leaf at the base of a flower stalk, flower cluster, or inflorescence.

 

Calyx

The group of outer floral leaves (sepals) below the petals, occasionally forming a tube.

 

Cyme

A branched, flat-topped or convex flower cluster in which the terminal flower opens first and the outermost flowers open last.

 

Cypsela

A dry, one-chambered, single-seeded seed capsule, formed from a single carpel, with the seed attached to the membranous outer layer (wall) only by the seed stalk; the wall, formed from the wall of the inferior ovary and also from other tissues derived from the receptacle or hypanthium, does not split open at maturity, but relies on decay or predation to release the contents.

 

Involucre

A whorl of bracts beneath or surrounding a flower or flower cluster.

 

Pappus

The modified calyx composed of awns, scales, bristles, or feather-like hairs in plants of the Asteraceae family.

 

Phyllary

An individual bract within the involucre of a plant in the Asteraceae family.

       
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Plant

  prairie ironweed (ssp. fasciculata)   prairie ironweed (ssp. fasciculata)
       
  prairie ironweed (ssp. fasciculata)    
       

Inflorescence

  prairie ironweed (ssp. fasciculata)   prairie ironweed (ssp. fasciculata)
       
  prairie ironweed (ssp. fasciculata)   prairie ironweed (ssp. fasciculata)
       

Flowers

  prairie ironweed (ssp. fasciculata)   prairie ironweed (ssp. fasciculata)
       
  prairie ironweed (ssp. fasciculata)    
       

Leaves

  prairie ironweed (ssp. fasciculata)   prairie ironweed (ssp. fasciculata)
       
  prairie ironweed (ssp. fasciculata)    
       

Stem

  prairie ironweed (ssp. fasciculata)   prairie ironweed
       

 

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