common sunflower
Family
AsteraceaeScientific Name
Helianthus annuus
Other Common Names:
annual sunflower
sunflower
wild sunflower
Synonyms (former Scientific Names):
Helianthus lenticularis
Helianthus aridus
Habit
Wild sunflower can complete its life cycle in as little as 60 days and can get from 8-15 ft tall. These plants tolerate heat and drought, but perish after the first frost. Blooms first appear in early summer and continue into early fall.
Leaves
When young, the seedlings are bright green and the width is double the length. Large, rough-hairy oval to heart shaped leaves; lower leaves opposite and chordate, the upper, smaller and narrower. The stems are sometimes branched, and the hairs on the stem are coarse. Mature leaves can be 3 or 6 inches (8-15 cm) to 1 foot (30 cm) across, usually with rough hairs.
Identifying Characteristics
The flower heads start out facing the east in the morning, and end up facing the west at the end of the day, following the sun.
Flower Seed Head
There will be 1-12 flowers that bloom during the summer to early fall. Large, gold, red-brown and yellow flower heads 3-12 inches across. Most have yellow ray florets and purplish brown disk florets. The ray florets of sunflowers are sterile, and only the disk florets produce seeds.
Seed Fruit
The seed can be seen in the center of the flower very easily. Fruit is a dry, dark casing with white stripes enclosing a white seed; flattish but plump.
Where Found
Prairies and dry, open areas, and is sometimes a weed in cultivated fields and pastures.
Growth Habit
upright and nonwoody
Thorns or Spines
not present
Approximate Flower Diameter
larger
Dominant Flower Color
yellow
Flower Symmetry
Varies:
radial symmetery,
bilateral symmetry
Leaf Hairs
has hairs
Leaf Arrangement
opposite
Leaf Margin
serrated
Leaf Structure
simple
Leaf Stalk
shorter than leaf
Stem Hairs
has hairs
Stem Cross Section
round or oval
Milky Sap
not present
Root Structure
taproot
Life Cycle
summer annual
Ochrea
present
Plant Type
Herb