Rydberg’s sunflower

(Helianthus nuttallii ssp. rydbergii)

Conservation Status
Rydberg’s sunflower
  IUCN Red List

LC - Least Concern


N3N5 -Vulderable to Secure

S3 - Vulnerable


Special Concern

Wetland Indicator Status
  Great Plains

FACW - Facultative wetland


FACW - Facultative wetland

  Northcentral & Northeast

FACW - Facultative wetland


Rydberg’s sunflower is an erect perennial forb that rises on one or a few stems from a short, branched rhizome. It can be from 40 to 100 tall, though in Minnesota it is usually no more than 80 in height.

The stems are erect, usually yellowish-brown or green, and sometimes covered with a whitish, waxy bloom (glaucous). They are sometimes branched near the top. Below the inflorescence they are usually hairless though they sometimes are sparsely covered with short, stiff hairs.

There are no basal leaves. Lower and middle stem leaves are opposite, those near the top are alternate. They are on 3 16 to long leaf stalks. The leaf blades are lance-shaped to nearly egg-shaped and flat, not folded longitudinally. They are 1½ to 8 long and 5 16 to 1½ wide. They are wedge-shaped at the base and taper to a point at the tip with straight sides along the tip. The upper surface is green and rough to the touch due to the presence if short, stiff hairs. The lower surface is covered with short or minute stiff hairs. The margins are untoothed or sparingly, shallowly toothed. The leaves have 3 main veins, a midvein and a pair of lateral veins that branch off the main vein above the base and arch upward.

The inflorescence is a solitary head or an open, branched cluster of 2 to 6 flower heads at the end of the stem. The flower heads are on stout, to 7 long stalks.

The whorl of 30 to 38 bracts at the base of the flower head (involucre) is hemispheric in shape and to ¾ in diameter. The bracts of the involucre are loose, spreading, almost hairless, lance-shaped to lance egg-shaped, and taper to a sharply-pointed tip.

The flower heads are 3 to 3½ wide with a to ¾ wide disk. There are 10 to 21 yellow ray florets and 60 or more yellow disk florets.

The fruit is an achene.




40 to 80


Flower Color


Yellow ray florets, yellow disk florets


Similar Species


Sawtooth sunflower (Helianthus grosseserratus) leaves are on longer stalks, ¾ to 2 long. The leaf blades are larger, 4 to 12½ long, and 1½ to 3½ wide. The margins are always toothed. The inflorescence has up to 15 flower heads. The involucre has 25 to 30 bracts. The flower head has 100 or more disk florets.


Moist to moderately moist. Prairies, wetland margins. Full sun.




Early August to mid-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.




Distribution Map



2, 3, 4, 5, 7, 28, 29, 30.









  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  


Asterales (sunflowers, bellflowers, fanflowers, and allies)  


Asteraceae (sunflowers, daisies, asters, and allies)  
  Subfamily Asteroideae  
  Supertribe Helianthodae  
  Tribe Heliantheae (sunflowers and allies)  
  Subtribe Helianthinae  
  Genus Helianthus (sunflowers)  
  Species Helianthus nuttallii (Nuttall’s sunflower)  

Subordinate Taxa






Helianthus nuttallii var. rydbergii

Helianthus rydbergii


Common Names


Nuttall’s sunflower

Rydberg’s sunflower













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.



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



Pale green or bluish gray due to a whitish, powdery or waxy film, as on a plum or a grape.



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



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

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    Rydberg’s sunflower   Rydberg’s sunflower  
    Rydberg’s sunflower      

Flower Head

    Rydberg’s sunflower   Rydberg’s sunflower  






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