stiff sunflower

(Helianthus pauciflorus ssp. subrhomboideus)

Conservation Status
stiff sunflower (ssp. subrhomboideus)
  IUCN Red List

not listed

     
  NatureServe

NNR - Unranked

SNR - Unranked

     
  Minnesota

not listed

     
           
           
 
Description
 
 

Stiff sunflower (ssp. subrhomboideus) is an erect, 12 to 48 tall, annual forb that rises on a single stem from long, thick, branched, creeping rhizomes. It often forms colonies.

The stems are erect, green or reddish-brown, and unbranched or sparingly branched near the top. They are rough to the touch due to a moderate to dense covering of short, stiff, ascending to spreading hairs. The stems are usually leafless near the top.

There are usually 5 to 10 leaf nodes below the inflorescence. Lower leaves are opposite, uppermost leaves are usually also opposite. Lower and middle leaves are rhombic egg-shaped to lance-linear, relatively thick, and flat, not folded longitudinally. They are 2 to 4¾ long and ¾ to 2 wide, 2½ to 8 times as long as wide. They are wedge-shaped at the base and taper to a blunt or sharp point at the tip with straight sides along the tip. The upper and lower surfaces are rough to the touch due to a moderate to dense covering of minute, stiff hairs. They are also sparsely to moderately covered with minute, stalkless, yellow glands. The margins are finely toothed to almost untoothed. The leaves have 3 main veins, a midvein and a pair of lateral veins that branch off the main vein well above the base and arch upward.

The inflorescence is sometimes a solitary head, usually an open cluster of 2 to 10 flower heads at the end of the stem. The flower heads are on stalks that are 13 16 to 4¾ long.

The whorl of bracts at the base of the flower head (involucre) is to in diameter. The bracts of the involucre are elliptic to egg-shaped and taper to a blunt or sharp point at the tip. The tips of the bracts are tightly appressed.

The flower heads are 1½ to 2½ wide, the disk is to 1 in diameter. There are 10 to 20 yellow ray florets and 75 or more reddish-brown to purple disk florets.

The fruit is an achene.

 
     
 

Height

 
 

12 to 48

 
     
 

Flower Color

 
 

Yellow ray florets, reddish-brown to purple disk florets

 
     
 

Similar Species

 
 

Stiff sunflower (Helianthus pauciflorus ssp. pauciflorus) tends to be taller, 32 to 60 in height. There are usually 5 to 15 leaf nodes below the inflorescence. The uppermost leaves are usually alternate. The lower and middle leaves are longer, 3 to 10 long. They are oblong lance-shaped to narrowly egg-shaped and taper to a sharp point at the tip with concave sides along the tip.

 
     
 
Habitat
 
 

Dry to moderately wet. Prairies, upland forest openings, pastures, railroads, roadsides.

 
     
 
Biology
 
 

Flowering

 
 

July to September

 
     
 

Pests and Diseases

 
 

Sunflower bullet gall midge (Pilodiplosis helianthibulla) makes ¼ in diameter, almost globe-shaped galls on the leaves of plants in the genus Helianthus.

 
     
 

Defense Mechanisms

 
 

The roots exude chemicals that inhibit seed germination and growth of young plants. When in a dense colony, these chemicals may cause the inner plants to die, leaving a ring of living plants.

 
     
 
Use
 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

3, 4, 7, 28.

 
  7/15/2020      
         
 

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 Asteroideae  
  Supertribe Helianthodae  
  Tribe Heliantheae (sunflowers and allies)  
  Subtribe Helianthinae  
  Genus Helianthus (sunflower)  
  Species Helianthus pauciflorus (stiff sunflower)  
       
 

The species name pauciflorus means few-flowered.

 
 

 

 
 

Subordinate Taxa

 
 

 

 
       
 

Synonyms

 
 

Helianthus laetiflorus var. subrhomboideus

Helianthus pauciflorus var. subrhomboideus

Helianthus rigidus ssp. laetiflorus

Helianthus rigidus var. subrhomboideus

Helianthus rigidus ssp. subrhomboideus

Helianthus subrhomboideus

 
       
 

Common Names

 
 

few-leaved sunflower

prairie sunflower

stiff sunflower

 
       

 

 

 

 

 

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.

 

Allelopathy

The release of a chemical toxin by one plant to inhibit the growth or germination of nearby competing plants.

 

Bract

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

 

Involucre

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

 

Linear

Long, straight, and narrow, with more or less parallel sides, like a blade of grass.

 

Node

The small swelling of the stem from which one or more leaves, branches, or buds originate.

 

Rhizome

A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.

       
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Plant

  stiff sunflower (ssp. subrhomboideus)   stiff sunflower (ssp. subrhomboideus)
       
  stiff sunflower (ssp. subrhomboideus)   stiff sunflower (ssp. subrhomboideus)
       

Flower Head

  stiff sunflower (ssp. subrhomboideus)   stiff sunflower (ssp. subrhomboideus)
       

Involucre

  stiff sunflower (ssp. subrhomboideus)    
       

Leaves

  stiff sunflower (ssp. subrhomboideus)    
       
       

 

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