Helianthus petiolaris

Species category

Weed

Common name

prairie sunflower, showy sunflower

Diagnostic characters

Planting unit

AcheneAchene:
A dry, hard, one-chambered, one-seeded indehiscent fruit, as in buckwheat (Fagopyrum) or sunflower (Helianthus). The fruit wall is not united with the seed coat.

Shape

ObovateObovate:
Inverted egg shaped with apical end the broadest.

Size

  • Length 4–5.5 mm 
  • Width 2–2.5 mm 
  • Thickness 0.6–0.8 mm 

Color

Gray with black mottling

Texture

Smooth and pubescentPubescent:
Having hairs.

Other structures

Small apicalApical:
The distal end of the fruit or seed away from the point of attachment or attachment scar.
collar

Identification notes

Helianthus petiolaris (on the right): AcheneAchene:
A dry, hard, one-chambered, one-seeded indehiscent fruit, as in buckwheat (Fagopyrum) or sunflower (Helianthus). The fruit wall is not united with the seed coat.
is obovateObovate:
Inverted egg shaped with apical end the broadest.
and compressed. Markings similar to Helianthus annuus (wild) (center), but the size is somewhat smaller, and the pubescence is longer and conspicuous.

Noxious weed seed categories

Not listed

AOSA examination list

Not included

Nomenclature

Family

Asteraceae

Valid name

Helianthus petiolaris Nutt.

From Left to Right: 1.  Helianthus annuus  (cultivated) 2.  Helianthus annuus  (wild) 3.  Helianthus petiolaris . Smooth and pubescent achenes. 
From Left to Right: 1. Helianthus annuus (cultivated) 2. Helianthus annuus (wild) 3. Helianthus petiolaris. Smooth and pubescent achenes. 
 Helianthus petiolaris.  Gray achenes with black mottling.
Helianthus petiolaris. Gray achenes with black mottling.